2013SummaryThis paper contributes to the debate about which factors determine the institutional quality of coun-tries. it uses explanatory economic, socio-political and cultural variables for three sub-samples ofcountries with different income level. The results validate the hypothesis that establishes there is notan only valid model of institutional quality for all countries. moreover, the limited explanatory ca-pacity of the model for the low-income level sub-sample of countries has motivated the incorpora-tion of other variables related to colonial origins, geographical location or life expectancy. The re-sults validate the theoretical arguments that propose the use of these variables