A lot of Human Reliability Analysis (HRA) methods calculate human error probability (HEP) based on different performance shaping factors (PSF). In calculating HEP, interdependency is generally ignored or addressed through varying parameters in linear or loglinear formulas [Groth 2009]. These dependencies could be more precisely represented by a qualitative model of PSF relationships. The aim of this paper is to describe the interdependence of the factors affecting human reliability using the method of qualitative modeling. Interdependencies between factors were based on different investigations. Appropriate qualitative relations were chosen for each pair of factors, and using a specific computer program, different scenarios were created.