Different types of fertilizers, such as chemical fertilizers, organic fertilizers and natural fertilizers are available on the market. The type of fertilizer has a large impact on plant production quality. The aim of this study, which was conducted under field conditions in the village of Jurumleri near Skopje, North Macedonia, was to investigate the influence of the application of two different types of fertilizers on leaf area and stomatal density in potato. The influence of the microbiological fertilizer Slavol and the organic fertilizer Biohumus was investigated. Also, a control plot without any fertilizer was used. A statistical tool (ANOVA test) was used for data analyses. The results showed that a statistically highly significant difference in average leaf area was found between plants treated with Slavol and plants treated with Biohumus (p<0.001). Also, a statistically highly significant difference was detected in stomatal density between plants treated with Slavol and control plants (p<0.001). A very significant difference was noticed between plants treated with Slavol and plants treated with Biohumus (p<0.01). The microbiological fertilizer Slavol showed better results than Biohumus in our research.