Characteristics of successional plant stages were specified, analyzed and compared in Cocobolo Natural Reserve in the upper Mamoní watershed, district of Chepo. Four sites with different ages (2, 7-10, 30-60 and 100 years old) were chosen, where the first and the last site were used as controls. Four plots of 25 x 40 m in each site were established. Data of trees with the following parameters: high of trees, strata, basal area and number of trees, were taken. ANOVA was used to verify significant differences between studied parameters. DUNCAN test was used to determine differences between treatments. A total of 132 woody species were inventoried, where the fourth sites presented the highest number of species. Number of trees, strata, species and basal area got higher progressively according to succession stages.