A study was carried out to determine the relationship between diameter structure and abundance in a low terrace forest in the district of Mazán, Loreto, Peru. The dasometric data were obtained from the logging permit of the native community León Isla of the operational plan 01 (PC 01). A total of 1123 trees were recorded, belonging to five species, four botanical families and four genera. A quadratic allometric model was applied to adjust the diameter structure and abundance, with results of R=0,620, adjusted R2=0,429, SEE=0,359 and residual=0,515. For the species Maquira coriácea, the adjusted quadratic model showed an R=0,620, adjusted R2=0,430, SEE=0,250 and residual=0,250. The highest abundance was found in diameter structures smaller than 50 to 70 cm (3,69 trees/ha), while diameter structures larger than 80 to 100 cm showed the lowest abundance (1,04 trees/ha). The Pearson correl...