Objectives: Good ventilation is more important in hospitals than in many other buildings. The objective of this study was to evaluate the effect of the condition, performance and modernity of ventilation systems on the perceived indoor air quality (IAQ) and the indoor air-related symptoms of hospital personnel. Materials and Methods: An inspection and evaluation graded on a 1 to 3 scale of the condition, performance, and modernity of the ventilation systems was carried out in ten central hospitals in Finland. The perceived IAQ and the related symptoms were collected by means of an indoor air questionnaire survey among the workers in these hospitals. Results: The condition, performance and modernity of the ventilation systems were good in 40% of the hospitals included in the research and poor in another 40% of them. In hospitals where the majority of the ventilation systems were assessed to be good, the prevalence of the indoor air-related complaints and symptoms was lower than in hospitals where the majority of the ventilation systems were assessed as needing extensive repairs. Conclusions: The condition and performance of the ventilation systems in hospitals had a significant impact on the perceived IAQ and the symptoms observed among the employees in Finnish hospitals. Therefore, it is important that hospital ventilation systems are maintained properly and regularly. Furthermore, they should be renovated, at the latest when their technical lifespan expires.