The objective of this study is to describe the relationships between grandchildren and their favourite grandparents, by studying the socialization styles used by latter and the shared activities undertaken. The participants were 360 children between 10 and 12 years old, who completed the grandparent-grandchild relationship questionnaire of Rico, Serra and Viguer (2001) and the socialization questionnaire of Rey and Ruiz (1990). The results demonstrate the importance of gender and family line in the selection of the favourite grandparent, differences being shown in the types of shared activities and in socialization styles. It is concluded that in the majority of cases the profile of the favourite grandparent is the maternal grandmother, retired or a house wife, aged between 60-70, who lives in the same city as his/her grandchild, and who has contact with them several times a week. Furthermore, favourite grandparents get more involved with granddaughters than with grandsons, both in support and care activities and in cultural-recreational activities, and they primarily employ a democratic style. However, there are differences depending on the gender of the grandchild, with democratic principles being used more with girls and authoritarian ones with boys.