fragmentation of data in oracle 10g

Good afternoon folks,

I have a client who is concerned that the recent poor performance on some databases is due to data fragmentation.

I am trying to convince the client that reorging the data or indexes will have little effect. Am I right?

We have segment space management on our tablespaces and locally managed tablespaces.

So in my view we are handling space far more efficiently than previously.

Are there some fragmentation issues that I should check out or should we be looking somewhere else for performance issues.