An important amount of research has been devoted to conceptual model validation, that is, to check whether a conceptual model correctly and adequately describes the users' intended needs and requirements. In this paper we present a new approach to model validation. We define a set of desirable properties that a conceptual model should satisfy and we show how the accomplishment of all these properties can be checked in a uniform way by means of planning. Our approach is independent of any particular planning method and it extends the facilities of the methods developed so far.