Given two cp-functions F and G we consider the largest cp-function H = F 0 G such that the
Y o u m -t y p e inequality H(XY) F ( x ) + G(Y)holds for all x, y > 0. We prove an equivalence theorem for F @ G with the best constants and, for the special case when F and G are log-convex and satisfy a certain growth condition, a representation formula for F @ G. Moreover, further properties and examples are presented and the relations to similar results are discussed.