In the current deforestation context, agroforestry is increasingly considered in the tropical zone for its potential contribution to biodiversity conservation. In Guinée Forestière (Guinea, West Africa), coffee-based agroforests are currently expanding on agricultural land around most villages. To assess the biodiversity potential of these agroforests, we compared their tree structure and diversity with those of a neighbouring natural forest. Eighty plots were sampled with a variable-area transect method (60 agroforests plots distributed into 3 village territories, and 20 natural forest plots). The structure of coffee-based agroforests showed obvious signs of farmers¿ management: for example, the density of mature trees was significantly lower than in natural forest and most juvenile trees were eliminated and replaced by coffee trees. However, sapling density was not significantly different than in the natural forest. Tree species richness and diversity in the agroforests were also lower than in natural forest but much higher than in any other agricultural or agroforestry landuse system. These results are close to those obtained in the coffee-based agroforests from Central America, confirming that agroforests retain many forest species that could play a key role in the conservation of regional forest-tree diversity. (Texte intégral)