Abstarct: Geopedology is a systematic approach to analyze the influence of the geomorphic levels on soil mapping. This approach makes it possible to generalize the soil survey results in one geomorphic unit to the other similar units of the same area that consequents in reducing the time and costs of soil survey. The main question in this regard is to what extent the soil data generalization can be valid? To answer this question the effect of the mapping scale, landform and kind of the soil classification system on the reliability of the geopedologic approach were studied in an area of about 1600 ha on the northeast of Damavand. For this purpose, the geomorphic units were determined by interpreting the 1:55000 and 1:40000 scale air photos of the study area, separately. In the next step, two similar districts named A and D were selected in piedmont landscape unit and two similar districts named B and C were selected in hill landscape unit as well. Afterward, 13 and 22 pedons were described and sampled in four selected districts of 1:55000 and 1:40000 scale maps, respectively. The pedons were classified up to the family level according to Soil Taxonomy (USDA, 2010) and up to the subunit level (including suffix and prefix qualifiers) baxsed on WRB (FAO, 2007) soil classification systems after physical and chemical analysis on all of the pedons’ master horizons. Finally, relative and Surndsun indices were used to analyze and compare the soil classifications of similar studied geomorphic units in two mapping scales, separately. The results indicated to the significant effect of mapping scale on the geopedologic approach so that the two taxonomic similarity indices for the same geomorphic units and in all levels were lower in 1:40000 scale than the 1:55000 scale for all studied pedons. Since geopedology approach is suitable for semi-detailed to reconnaissance studies, the results of this study showed mapping scale was effective in semi-detailed scales, as well. The results also show the similarity was higher among the pedons in piedmont than hill. In the other word, the geopedologic approach was more efficient for mapping the piedmont landscape unit. It was probably due to the less variations of slope in piedmont comparing to hill. Furthermore, despite the ability of WRB classification system to better depict the reality of soil characteristics in the field, Soil Taxonomy system was more successful to predict the similarity among geopedologic units. It is likely because of the six-level hierarchical origins of both Soil Taxonomy classification system and the geopedologic approach that made them correlate more easily. It is suggested to add a newer and more precise category to the geopedologic approach naming “landform phase” in order to increase the efficiency of this approach when it is going to use for semi-detailed and larger scales soil survey.