A cutting tool includes a cutting insert releasably retained therein. The cutting insert has at least a first non-planar side surface, which includes a planar portion that is recessed with respect to other portions of the side surface such as the cutting edges thereof. The planar portion may be spaced apart from the cutting edges associated with that side surface. The planar portion is the only portion of the side surface to engage an abutment region or regions of a supporting wall of the cutting tool. The cutting insert may be double-sided, and include a second, opposing side surface having a respective planar portion formed therein, wherein the two opposing side surfaces interchange positions upon indexing of the cutting insert. The planar portion of the second side surface, which does not engage the abutment region or regions of supporting wall, does not interfere with the functionality of the cutting insert.