When does an HR ask "what are your expectations regarding job position" in an interview? Should you answer honestly or professionally?

Combination of honesty and professionalism

Professionally , The employer can understand the professional approach of the candidates ,  it  also reveals  that that candidate  reaction towards a Company standard.   

The last person you dont want to lie is yourself, I personally feel we must have a good blend of Both honesty and Professionalism in ones behaviour and attitude while attending any interview

You should answer professionally.

Remember you are trying to sell yourself to the company; how many salesmen you know that they answer honestly instead of professionally to close the sale!