Exposure to secondhand smoke (SHS) is a serious threat to public health, and a significant cause of lung cancer and heart disease among non-smokers. Even though Greek hospitals have been declared smoke free since 2002, smoking is still evident. Keeping the above into account, the aim of this study was to quantify the levels of exposure to environmental tobacco smoke and to estimate the attributed lifetime excess heart disease and lung cancer deaths per 1000 of the hospital staff, in a large Greek public hospital. Environmental airborne respirable suspended particles (RSP) of PM2.5 were performed and the personnel's excess mortality risk was estimated using risk prediction formulas. Excluding the intensive care unit and the operating theatres, all wards and clinics were polluted with environmental tobacco smoke. Mean SHS-RSP measurements ranged from 11 to 1461 microg/m3 depending on the area. Open wards averaged 84 microg/m3 and the managing wards averaged 164 microg/m3 thus giving an excess lung cancer and heart disease of 1.12 (range 0.23-1.88) and 11.2 (range 2.3-18.8) personnel in wards and 2.35 (range 0.55-12.2) and 23.5 (range 5.5-122) of the managing staff per 1000 over a 40-year lifespan, respectively. Conclusively, SHS exposure in hospitals in Greece is prevalent and taking into account the excess heart disease and lung cancer mortality risk as also the immediate adverse health effects of SHS exposure, it is clear that proper implementation and enforcement of the legislation that bans smoking in hospitals is imperative to protect the health of patients and staff alike.