In most computer vision applications, the extraction of key image features, whatever the transformations applied and the image degradations observed, is of major importance. A large diversity of approaches has been reported in the literature. This chapter concentrates on one particular processing frame: the moment-based methods. It provides a survey of methods proposed so far for the derivation of moment invariants to geometric transforms and blurring eects. Theoretical formulations and some selected examples dealing with very dierent problems are given.