CPM?, CPC? or Both - iPhone advertising

[BEDIR]

Hi - im new to iPhone development and am building a very ambitious app and advertising revenue is critical to my project.

Is there any advertising network that pays by true CPM rather than CPC (and eCPM) or a combination of both?

EDIT: Like if i have very few clicks but high number of impressions, do i still get paid?

any help please, thanks