Yes. Being named as executor in someone's Will just means that you are the person named to administer their estate if you are willing and able to do so (i.e. you are not disabled or incapacitated). You are also not obligated to serve as executor of the Estate after that person passes away if you just do not want to (i.e. you don't have time, you live far away, etc.).
Typically, the executor clause in the Will includes more than one named executor, either in succession or as co-executors. If you are named in a succession, the next named person would then be able to step in if he is willing and able to do so. If he is not, then it again follows the succession. In the case of co-executors, the other named person would be able serve alone if able and willing.
If you are unable and/or unwilling, you must sign a Renunciation to renounce your right to serve and request that the Register of Wills instead appoint the next named person.
Before renouncing your right to serve, you should always consult with a probate and estate administration attorney.