You would generally write is as : Executive Assistant to the CEO It is certainly a widely used term. An executive assistant is always an executive assistant to someone, so it is best to follow that with the person to whom you are executive assistant.

The term "Executive Assistant to Chief Executive Officer" is appropriate and expected in a resume of someone seeking a similar or related position. 'Executive Assistant' is a much more general term. For instance, you could be an executive assistant to the CEO (Chief Exec. Officer), but it is also possible you could be an executive assistant to someone who is much lower in the management structure - ie. a middle manager. When you are writing a resume if would be much better to fully mention the type of executive assistant if that position was for someone high. ie. "Executive Assistant to the CFO (Chief Financial Officer)", "Executive Assistant to the Director", etc.