The R package ThreeWay is presented and its main features are illustrated. The aim of ThreeWay is to offer a suit of functions for handling three-way arrays. In particular, the most relevant available functions are T3 and CP, which implement, respectively, the Tucker3 and Candecomp/Parafac methods. They are the two most popular tools for summarizing three-way arrays in terms of components. After briefly recalling both techniques from a theoretical point of view, the functions T3 and CP are described by considering three real life examples.