Aim: The aim of this study was to report and contrast the aspects of two therapies considered by clients and therapists to be most and least useful. Method: In the UK Alcohol Treatment Trial (UKATT), 742 clients were treated by 49 therapists with up to three sessions of motivational enhancement therapy (MET) or up to eight sessions of social behaviour and network therapy (SBNT). After each treatment session, clients and therapists were asked to independently complete two sentences, one inviting a statement about the 'most useful' and the other about the 'least useful' thing that had happened during the session. Results: The proportion of 'most useful' sentences completed was greater than the proportion of 'least useful' and equally so for MET and SBNT. The content of comments was significantly different for the two treatments: more comments on social aspects followed SBNT and more motivational comments followed MET, with larger numbers of comments following both treatments that were more general. Clients more often completed 'most useful' sentences than therapists and less often completed 'least useful' sentences. There were a number of differences in the content of their comments: notably more 'most useful' client comments about talking to their therapists, and more therapist comments about client engagement. Conclusions: MET and SBNT left distinct impressions on the participants immediately following treatment sessions, adding to the evidence that they are different treatments, and hence deepening the mystery about why outcomes following the two treatments were so similar [UKATT Research Team. (2005) Br Med J 331: 541-58].