This article presents some of the theoretical and methodological considerations in studying religious and cultural diversity in Finnish, Swedish and Estonian comprehensive schools. The perspective arises from our experiences of carrying out an international comparative research project looking at pupils´perspectives to diversity in the educational settings and their wider everyday environments. The data were gathered in diverse comprehensive school contexts across Sweden, Estonia and Finland. The article illustrates several important issues that are often lacking in the studies in this area and need to be accounted for when examining cultural and religious diversity in the schools and the everyday lives of children and youth.