When you create a cylinder with any cap segments in 3ds Max your cylinder will have a single vertex pole in the middle of the cap. For example, if you create a 24 sided cylinder with a cap segment there will be a single vertex with 24 attached edges. This is not desirable as it results in a lot of triangles that do not smooth as well as quads.
This quick tip will show you how to change that cap segment into all quads suitable for smoothing. If you would like to create a cap that is rounded and not flat, then you can head over to my other tutorial to create a quad topology sphere.