ObjectiveCompared to community adolescents (COM), adolescents placed in residential care (RC) or late adopted (LA) appear to show more emotional–behavioural problems. They also appear vulnerable in variables linked to emotional–behavioural problems, such as insecure–disorganized attachment and alexithymia. This study employs a mixed‐method multi‐informant approach to (1) compare adolescents placed in RC, LA and COM in emotional–behavioural problems, attachment and alexithymia and (2) investigate relationships and interplay of attachment and alexithymia concerning emotional–behavioural problems in these three groups.MethodParticipants were 174 adolescents (50 RC, 33 LA and 91 COM; Mage = 15, 53% boys and 47% girls). Adolescents' internalizing and externalizing problems were assessed through both caregiver‐reported and self‐reported questionnaires, while attachment and alexithymia were assessed with a mixed method, using interviews and self‐report questionnaires.ResultsThe results showed RC adolescents as more vulnerable in all variables, while LA and COM did not differ. Accounting for the group, attachment and alexithymia cumulatively predicted 25–43% of internalizing problems, and 19–43% of externalizing problems depending on the method of assessment or problems' informant (all p < 0.01). Alexithymia was both an independent predictor and interacted with preoccupied attachment in predicting internalizing problems, while no predictors were isolated for externalizing ones, and the group never indicate an effect on problems' rates.ConclusionsThe authors discuss the utility to maintain a research focus on attachment and alexithymia, also suggesting future directions of research. A need to determine potential distortions of results because of problems' informant and method of assessment is also highlighted.