L.G.
Slyvia,
we were having the same problem with my 3 year old daughter. I finally just left it up to her whether she wanted to take a nap or have "quiet time" in her room. It worked for us. Now, she decides if she wants to take a nap (usually she takes one now twice a week.) The rest of the time it is quiet time, where she reads books or lays down but doesn't have to sleep.
On the days she does not take a nap, she goes to bed earlier, and she is now sleeping through the night. She used to get up at least 2 -3 times a night for something (any reason, actually) and it was driving me crazy. It stopped once we dropped the mandatory nap. She was a little cranky without the nap for the first two weeks, but then she adjusted and is sleeping through the night again! Good luck!