This paper focuses on the development of Prosodic Word shapes in Catalan, a language which differs from both Spanish and English in the distribution of PW structures. Of particular interest are the truncations of initial unstressed syllables, and how these develop over time. Developmental qualitative and quantitative data from seven Catalan-speaking children reveal that maximality constraints are active at two stages, namely, the moraic trochee stage, and the bisyllabic foot stage. One of the noteworthy differences between Catalan and Spanish is the rate of acquisition of weak initial syllables in WS words, as Catalan learners omit initial syllables in WS target iambs for a significantly longer time than Spanish learners, despite the fact that Catalan is a language where the bisyllabic iambic WS pattern is more frequent than in Spanish. We claim that this asymmetry in the course of development of PWs can be attributed to the frequency of exposure to different metrical models. In Catalan (and also in English), the high frequency of CVC structures boosts the availability of the moraic trochee in initial stages. Thus the data provide crucial evidence that children at early stages of PW production are especially sensitive to the frequency distribution of foot structure in the input. In general, the behavior of Catalan PW acquisition significantly supports the idea that the course of PW development is strongly influenced by language-specific distributions of prosodic structures (especially feet) in the target language (see Demuth, 1996a, 2001a, 2003; Lleo, 2002; Prieto, Bosch-Baliarda, & Saceda-Ulloa, 2005; and Zamuner, Gerken, & Hammond, 2004, among others). (Contains 3 tables, 5 figures and 6 footnotes.)