In this research, soils with favourable climate for forest have been selected. They are located in high areas (1070 m and 825 m of altitude, respectively) of the central Spain, where less humid and less temperated climate facilitates the forest growth. The study focuses on soils under holm oak (Quercus ilex sp. Rotundifolia) of the Guadarrama Mountain and the Páramo, placed in the region of Madrid in Spain. In these places, the adequate conditions are given for the formation of an umbic or mollic epipedon, which are mineral horizons with a high content on organic matter. The Inceptisol of the Guadarrama Mountain has an umbric epipedon and it is influenced by different altitude, temperature, precipitation and parental material that the Mollisol of the Páramo, which has a mollic epipedon. Inceptisol and Mollisol are compared. They show a clear differentiation in their properties, mainly because of the influence of the parental material, being granite in the case of the Guadarrama Mountain Inceptisol under holm oak and lime in the Mollisol of the Páramo under holm oak. These research shows that the soil organic matter content is related to the soil properties, site characteristics and the environmental conditions. Soil organic matter in the surface horizon of Mollisol is more humificated than in the surface horizon of Inceptisol. In this horizon, the C/N ratio is lower in Mollisol than in Inceptisol and the pH and electrical conductivity are higher in Mollisol than in Inceptisol.