What is more challenging in lean journey? process improvement activities or mindset change of people?

I would go for process improvement. It can prove to the company "leaders" the benefits, therefore making easier to change their minds. Strong economical data/facts can persuade everybody!

lean is a calture so the most important is to change the pepol mindset Lean is same as a big wheel its diffcult to move it but when it start to rotate its become more diffecult to be stoped

The fact is you cannot perform improvement activities without changing mind set. So, IMHO "mindset changing" is more challenging and once mindset changes it is easy to perform "improvement activities".

However, if you try to perform improvement activities before changing mind set. It will become most challenging :)

Resistance to change is the most difficult part of LEAN journey. You might think of the best process improvements, but if no one agrees to follow these processes there will be no improvement at all. The great thing in LEAN approach is that, it involves team work. The more ideas are involved, the better, because people will be more proactive in a job in which they became a part of the ideas that improved it. 

Process Improvement activities are more important for Lean Journey as we know that Lean is continous improvement methology focused on managin process and improving them by comprsing them rather than forcing manpower. Lean imphasizes the prevention of waste, extra time, labor spent on producing a product or service that doesnt add any value to it. Whatever the output that is the result shown to customer not the way it has been produced so its better to produces by eliminating waste and time instead of spending on labor and cost.

No Doubt, changing peoples mindset is difficult and most important for acheiveing success in your lean journey. By success I mean making breakthrough improvements and sustianing these improvements in the long run. By saying this it doesn't mean that process improvement activities are not important. So its chicken and egg situation. For a successfull lean journey you need to have people mindset change and for mindset change you need to show process improvements. We need to address both. In the short term, at the start of the lean journey focus on process improvements as pilots, share the results, success stories with your stakeholders, communicate to all and these will help you to change peoples mindset in the long term. Remember if you are not able to change your peoples mindset then success will not be sustained and you will find difficult even to do process improvements.

Its the mindset of people.

As most of the people tends not to change and live their life in a comfort zone. 

mindset is the most important because it needs to change the mentality of people because education and understanding are essential for a successful lean implementation. The entire workforce needs to be educated in the principles of lean and how to apply them to their work and areas.  Education in lean tools can come later and should be targeted to avoid the syndrome of becoming bogged down in the application of the tool rather than the application of lean.

There is a deep suspicion that comes from a lack of understanding of lean principles and this leads to a lack of buy-in from those most needed in the process.

Education opens the door to understanding. Application helps people walk through the doorway. Familiarization helps them turn on the light and see the benefits.

Understanding the benefits of lean helps to drive the cultural of support for lean.

Support is needed at all levels of the organization in order for a lean implementation to succeed.  Lean is not a system that can be "enforced" from the top down or driven from the bottom up.

Lean is cultural change. It requires active support from all levels of the organization to create a sense of constant lean mindfulness.  This is a slow process in any organization and is doomed if there are no champions to keep it active in the mindset of the entire workforce.

Managing the change is the most difficult part. Changing the mindset of people is one of the most difficult challenge as it has to do with the personal choices and capabilities. To convince someone that increasing the efficiency of a process does not necessarily means that the organisation is going to go for a cut in headcount and that the value a resource renders to the company is demeaned is a daunting task. To keep it straight, if a consultant can manage/handle resistance to change, the battle is half won

The first step is change of the mind-set. Any concept, how-so-ever brilliant, that involves human intervention or participation, will only succeed if the humans believe in the concept.

As mentioned by other esteemed participants, change is difficult unless managed properly.

Resistance to change is a fact.

Buy-in of the top management and a clear change management strategy are key to changing the mind set.

Walk the walk, talk the talk and slowly, steadily you will notice a change in the mind set.

Once change in mind set sets in, all levels will start improving their own processes.

Ideas will flow from them of how to improve, eliminate waste, deliver better quality, satisfy customer.

Employees will start to own the process.

Changing mindset of people is more challenging  for Lean journey because people can think about continuous improvement only when they can cope up their mind with positive change.