In a mosaic landscape in Guadalajara province (central Spain) butterfly diversity was positively correlated with the area of woodland fragments and negatively correlated with fragment isolation, as measured by the amount of forest within 1 km of the study plots. Patchiness and diversification of vegetation structure also increased with fragment area, and were thought to contribute to explain higher butterfly diversity in relatively large fragments. Rounded shapes of fragments also benefited a higher butterfly diversity. Palabras clave: Butterfly, Forest, Fragmentation, Isolation, Mosaic, Vegetation