In the field of gender studies, differences in participation between men and women in the labour market are nobserved. Although the proportion of working women converges the male rate, the modes of working are different from female to male. It is said that women are increasingly working part-time, more rarely in leadership positions and rather in business sectors with lower earnings. Differences are then finally expressed by different income levels. This “gap” between mean incomes of men in comparison to woman is regularly called “GenderPay-Gap” or “Gender-Wage-Gap”. The Gender-Pay-Gap is used as an indicator for the measuring of the equality of payment between men and women. These unequal incomes result not only from a different wage, but also from a different offer of working hours. This paper approaches this subject by an empirical analysis for the field of self-employment, especially in the differentiation between professionals and tradesmen.