In the present research, the associations of various sociodemographic variables of the adult adoptee and the adoptive family, of the adoptive process and the family dynamics (family functioning and communication about adoption) with the level of differentiation of self and of attachment of adults adopted in Spain are analyzed. The study involved 50 adopted adults, national and international, of both sexes, between 18 and 51 years of age. To assess the variables, a self-made socio-demographic questionnaire, the Family Adaptability and Cohesion Evaluation Scale-20Esp, the Adoption Communication Scale-Spanish, the Differentiation of Self Scale and the Experiences in Close Relationships-Spanish questionnaire were used. The results showed that differentiation of self of the adopted adults was explained in 27% by family functioning and in 9% by communication about adoption with the mother. It was also observed that differentiation of self was predicted in 58% by avoidance, anxiety and family functioning. In addition, emotional reactivity was explained in 24% by family functioning, while emotional cutoff was predicted in 42% by age of adoption and family functioning. A moderation analysis did not find that family functioning moderated the relationship between age of adoption and emotional cutoff. On the other hand, anxiety was explained in 13% by cohesion, and avoidance was predicted in 9% by adoption age. Likewise, anxiety was explained in 22% by emotional reactivity, and avoidance was predicted in 58% by emotional cutoff. Finally, differentiation of self shared 50% of the variance with avoidance and anxiety. The relevance of the results are discussed.