background. insomnia is a frequent problem in people who suffer from mental illnesses. the nursing staff control and register whether or not patients sleep. the aim of this article is to analyze the concordance between the perceptions of the patients of a psychiatric unit on the quality of sleep, and the notes in this respect contained in the nursing records. methods. a comparative study between the answers given by the patients of our unit to 126 questions on insomnia on specific nights, and what was reflected in their nursing records. a reduced version of the athens insomnia scale (ais-5) was used. results. the average value obtained according to the patients answers was higher (worse sleep) than that given by the nurses, both globally and by item. the nursing records showed much lower values than those given by the patient; pearsons correlation analysis gave a coefficient of 0.26. analysis of the degree of agreement provided an index of 0.13 that does not differ significantly from nil agreement. conclusions. there is a difference between the nursing observations and the subjective sensations of the patients about how they sleep. they indicate that they sleep worse than the nursing records reflect. external observation and self-perception are not antagonistic aspects, but two complementary aspects of patients sleep.