The aim of this study was to adjust and select different probabilistic density functions to describe the diametric distribution of all species and the seven species with the highest importance value in a fragment of Mixed Ombrophilous Forest in Lebon Régis - SC. The data used to adjust the functions was obtained by simple random sampling in which the 20 plots were made using the fixed area method with dimensions of 10 x 50 m (500 m2) and the trees with a diameter at breast height ( ) greater than or equal to 5 cm were measured. The probabilistic density functions Normal Ln-normal Gamma Beta Exponential Weibull 3P Johnson's Sb Weber and Péllico Netto were adjusted using the Solver tool in MS Excel 2007 which uses the generalized reduced gradient (GRG) linear algorithm for parameter interaction. The selection criteria used were the Kolmogorov-Smirnov test and the fit and accuracy statistics.