The effect of vegetation on morphological soil features was examined by characterizing twenty-six sites in southwest Neuquén province, Argentina. Thirteen sites were under native vegetation Nothofagus forest and thirteen under Pinus ponderosa Dougl. Four representative soil profiles were compared, under both conditions, to establish it there were any relationships between vegetation change and soil porosity, soil water retention and soil structure. For each horizon, three samples were plotted for bulk density and three undisturbed samples for water characterization. Hydric constants were determined for disturbed and undisturbed samples. Hydric contents at low tension were made with tension tables, and others with a pressure plate extractor. Total porosity and pore size distribution (macropores and micropores) were determined. A change in soil structure from granular to massive was observed under ponderosa pine at all sites. No significant changes in bulk density and total porosity were detected between the vegetation conditions. The change in soil structure reflected the change in pore size distribution, increasing microporosity and decreasing macroporosity under ponderosa pine.