This paper deals with the gender gap in accessing and using financial services provided by mobile money and financial institutions. Using data from ECOWAS member countries, we applied the Fairlie decomposition method to estimate and decompose the gender gap. The results show that mobile money contributes to improving of the use of services compared to financial institutions. However, it also increases the gender gap in women's disadvantages in accessing and using these services. The difference in the level of education and income between males and females is the main factor explaining the gender gap.