The analyses presented in this paper come from a representative study 'Social Diagnosis' conducted in Poland. The specific models for each question were estimated using the logistic regression model. Findings: The research confirmed that individual personal characteristics do affect decisions that people make in everyday life. Each of the variables discussed in the paper affects solidarity. Similar to other studies, this study also shows that income, education, religion and a high number of friends increases solidarity, support to others. Unlike in many previous studies, it is indicated that men are more likely to engage in helping others. Undoubtedly, this is due to the specific socioeconomic conditions occurring in the postsocialist economy of a developing country. Practical Implications: In order to increase cooperation in different societies, people should be encouraged by the state to display appropriate behaviours, and factors influencing these behaviours should be supported. Due to the socioeconomic development of the country, the levels of income or education of individual residents can be influenced in the long run. However, increasing solidarity can also be influenced indirectly, for instance, by initiating actions that support social integration or social and professional activity of people. Originality/Value: It is a first article about solidarity based on the research conducted among more than 22,000 respondents. The results obtained in the article are slightly different from those presented in other studies. However, they appear to be characteristic of former socialist countries, because people in these countries, after 45 post-war years, need to change themselves in order to be more cooperative.