This study investigated the quality of documentation of post-operative nausea and vomiting (PONV) by comparing incidences collected by a research team with those reported routinely by nursing personnel. A total of 560 patients passing through an interdisciplinary recovery room were included in the study. The overall recorded incidence of PONV over 24 h was 30.7%, which was in agreement with the predicted value of 32% calculated using incidences from published randomized controlled trials. Out of the total number of 86 cases of PONV in the recovery room only 36 (42%) were detected by nursing staff. Similarly, out of the total number of 129 cases of PONV on the ward over 24 h, only 37 (29%) were recognized by nursing staff during routine care. In conclusion, PONV in routine clinical care is likely to be under-reported. To use PONV as a valid quality measure, patients need to be actively asked about nausea and vomiting at frequent intervals in a standardized fashion. A considerable proportion of patients experience PONV after discharge from the recovery room, so the assessment of PONV should cover at least 24 h post-operatively.