According to several clinical authors inspired by attachment theory, the concept of secure attachment can be viewed as overlapping with the therapeutic alliance. In this article, we illustrate the reasons why attachment patterns and the therapeutic alliance should be considered as two distinct but reciprocally related concepts. We present the Patient Attachment Coding System (PACS), a tool for the analysis of communication between patient and therapist, which allows to evaluate the patient’s pattern of attachment through the analysis of a transcript of a single therapy session. Research with the PACS shows that secure attachment enable greater emotional proximity to the other and a better ability to explore and
reflect on the individual’s internal states, while patterns of insecure attachment are seen to be associated with considerable difficulties in these areas. In this perspective, the individual differences found in the different attachment patterns correspond to distinct cooperative modalities, which globally represent the patient’s best collaborative efforts to convey their experiences in dialogue with the therapist. The use of PACS to monitor communication between patient and therapist can contribute to the understanding of the negotiation and co-construction of the therapeutic alliance, offering a promising new perspective for clinicians who are interested in enhancing the therapeutic power of the patient-therapist relationship.