Architectural patterns of eight Cecropia species were studied in Amazonian and Southeastern Brazil. Height, diameter, height of first branching, number of branches and leaves, leaf area, internode length and branching ratio were measured for undamaged trees. The Amazonian species C. concolor; C. palmata, C. purpurascens, C. ulei and C. sciadophylla were studied in Manaus. Cecropia galziovii, C. hololeuca and C. pachyshachya were studied in Linhares, Espirito Santo. All except C. hololeuca and C. sciadophylla are myrmecophytes. In both areas, size and architectural characters are displayed as a gradient from open habitats to forest. Cecropia hololeuca and C. sciadophylla are common in forests and had similar architectures, with low branching ratios, and a height of first branch of around 9 m, about 3 m higher than the other species. The branching pattern of both species and the maximum height recorded (approximate to 20-25 m respectively) allow them to remain in the canopy longer than the other Cecropia species. Cecropia concolor and C. pachystachya measure up to 13 m in height and are typical of open habitats. The remaining species occupy forest margins and are intermediates between these two extremes.1963215226