In this article the evolution of the structure of the ethnic space in Montréal is analyzed, for the period 1931-1971, with three-mode factor analysis. The results show the specificity of the residential behaviour of some minority groups with respect to dominant groups in particular that of Italians, Poles and Ukrainians. Consequently, the structure and evolution of ethnic space in Montréal is far more complex than the simple spatial differentiation between the French and other groups suggested by other studies.