Resumen
(1) The COVID-19 outbreak brought about several socio-economic changes and has had a negative impact on the mental health of people around the world. The aim of this study was to examine the correlation between health behaviours and dispositional optimism among nursing students in Poland, Spain and Slovakia during the COVID-19 pandemic. (2) The study was carried out in spring 2021 on a group of 756 nursing students in Poland (n = 390), Spain (n = 196) and Slovakia (n = 170). The diagnostic survey method was applied with the questionnaire technique, and the following standardised research tools were used: Life Orientation Test?Revised (LOT-R) and the Health Behaviour Inventory (IZZ). The survey was conducted in a mixed arrangement: in direct contact with the respondents in Poland and in Spain and online in Slovakia. (3) Significant differences were demonstrated in health behaviour preferences in students in Poland, Spain and Slovakia (F = 6.22; p < 0.002). The highest IZZ index was found in Spanish students (82.60 ± 13.65), while lower values were observed in Slovak (80.38 ± 13.74) and Polish (78.44 ± 13.47) students. The correlation between dispositional optimism and a positive attitude was the strongest in the Polish sample (r = 0.56; p < 0.001), at a high level in the Spanish sample (r = 0.53; p < 0.001) and at an average level in the Slovak sample (r = 0.48; p < 0.001). (4) 1. The study showed a moderating effect of the country of origin on the students? health behaviours. 2. Dispositional optimism is an important predictor of the students? health behaviours, regardless of the country of origin.