Confinement due to COVID-19 has had a worldwide impact. The aim of this study is to analyze psychological variables involved during lockdown of emerging adults (EA) and the adult population, and the differences between Spain and the Dominican Republic (DR). A convenience sample of 685 people was used. An ad hoc online survey measured sociodemographic variables, trust in the healthcare system, fear of COVID-19, acute stress, mindful trait, capabilities, difficulties and resilience. Significant differences by sex were found in acute stress and emotional difficulties and fear of COVID-19 (p<.01) greater in women than in men. Regarding the country of residence, they presented greater fear of disease and less confidence in the public health system in the DR (p<.01). Adults showed more fear of the disease (p <.05), a greater mindful trait and enhenced prosocial behaviors (p<.01). EA scored higher acute stress and emotional difficulties (p<.01). Linear regression analysis was performed, fear of COVID-19 was the best predictor of acute stress. In conclusion, the results suggest the need for more information on differences by both nationality and age in the impact of unique stressors such as COVID-19 in order to create effective prevention programs