An analysis of some parameters of vegetation structure (coberture -%-, density and specific diversity) is presented for plant formations in the Mocagua island (Colombian Amazonia). The structure of the vegetation types ranging from simple river beach zone, aquatic and floodplain environments, to complex arrangement in forest formations. The average number of individuals with DAP > 10 cm (58/0.1 ha) is lower than other similar regions. In addition, we describe the types of vegetation founded according with floristic affinities, wich is related to the water content in the sustrata.Tha natural vegetation comprise from aquatic communities of Oxyearyum eubense - Pontederia rotundifolia, to continental ones of Rheedia madruno- Palieourea eroeea, Triehilia pallida - Sommera sabiceoides, phases of Montriehardia arboreseens and Ceeropia latiloba, Paspalum repens and Ceeropia latiloba, and Leptochloa seabra and Torulinium maeroeephalum.