BACKGROUND: International variation in compulsory admissions to psychiatric care has mainly been studied in terms of civil commitment rates. The objectives of this study were to compare and analyse the levels of perceived coercion at admission to psychiatric in-patient care among the Nordic countries and between centres within these countries, in relation to legal prerequisites and clinical practice. METHOD: From one to four centres each in Denmark, Iceland, Norway, Finland and Sweden, a total of 426 legally committed and 494 formally voluntarily admitted patients were interviewed within 5 days from admission. RESULTS: The proportion of committed patients reporting high levels of perceived coercion varied among countries (from 49% in Norway to 100% in Iceland), and in Sweden, only, among centres (from 29 to 90%). No clear variations in this respect were found among voluntary patients. A wide concept of coercion in the Civil Commitment Act and no legal possibility of detention of voluntary patients were associated to low levels of perceived coercion at admission among committed patients. CONCLUSION: For committed patients, differences in national legal prerequisites among countries were reflected in differences in perceived coercion. The results from Sweden also indicate that local care traditions may account for variation among centres within countries.