Even though previous attachment taxometric studies supported the conclusion that attachment is rather dimensional than categorical construct, they also did not provide consistent support against categorical approach. Addressing limitations of previous taxometric studies on adult attachment, we asked two research questions: Is attachment as measured by the Adult Attachment Scale (AAS) categorical or dimensional? What is the predictive validity of categorical and dimensional approaches? To answer these questions, data of the AAS from 869 parents, 575 adolescents, and 500 grandmothers from the same families in Poland were analyzed. Taxometric analyses were replicated across three generations providing weak evidences to support the dimensional approach. Clustering methods provided an additional support revealing that empirically derived categories of attachment are based on security level but not on qualitatively different attachment patterns. Analyses testing predictive effects of categorical compared to dimensional approaches to attachment assessment revealed that a dimensional approach is more valid than a categorical approach in testing hypotheses related to the intergenerational transmission of attachment.