The aim of this study was to describe and compare the knowledge of registered nurses (RNs), assistant nurses (ANs) and student nurses (SNs) about preventing pressure ulcers (PUs). PU prevention behaviours in the clinical practice of RNs and ANs were also explored. A descriptive, comparative multicentre study was performed. Hospital wards and universities from four Swedish county councils participated. In total, 415 participants (RN, AN and SN) completed the Pressure Ulcer Knowledge Assessment Tool. The mean knowledge score for the sample was 58·9%. The highest scores were found in the themes ‘nutrition’ (83·1%) and ‘risk assessment’ (75·7%). The lowest scores were found in the themes ‘reduction in the amount of pressure and shear’ (47·5%) and ‘classification and observation’ (55·5%). RNs and SNs had higher scores than ANs on ‘aetiology and causes’. SNs had higher scores than RNs and ANs on 'nutrition'. It has been concluded that there is a knowledge deficit in PU prevention among nursing staff in Sweden. A major educational campaign needs to be undertaken both in hospital settings and in nursing education.