Three boys (an extremely preterm, a moderate preterm twin and a full-term toddler; all 12 to 15 months old) were selected from a large sample to investigate mechanisms of parent-child attachments, specifically of babies born preterm. Attachments were observed at home with the Attachment-Q-Sort (AQS) as well as in the lab with the Strange Situation (SS). Both AQS and SS were used twice for each boy, separately with his mother and father. Whereas the SS was efficient in analyzing basic attachment repertoire, levels of arousal and its regulation, the AQS depicted general characteristics of the attachments. Results revealed constraints in use and provision of the secure base function which were only able to be demonstrated in the SS for father-child dyads of the preterm boys. This suggests that restriction in attachment repertoire, as well as inadequate paternal responses, led to descriptions of insecure attachments, whereas AQS-based assessments of the same dyads showed secure attachments.