Aims and method To assess the patients' most influential concerns regarding long-acting injectable antipsychotics (LAIs) and mental health professionals' preconceptions about these concerns. For both groups, to assess the level of knowledge about LAIs. This cross-sectional study used semi-structured interviews of patients with schizophrenia or schizoaffective disorder (n = 164), nurses (n = 43) and physicians (n = 20). Results The mental health professionals overestimated many of the patients' fears of LAIs, and the expressed fears exceeded the actual experiences of patients already on LAIs. Acceptance to switch to LAIs was associated with shorter time from diagnosis. Nurses and patients disclosed limited knowledge of antipsychotics. Clinical implications Physicians and nurses should aim to identify the individual patient's concerns about LAIs in the discussion about choice of antipsychotic treatment early in the course of illness.