Introduction: This article is the first part of considerations on the concept of optimism and its impact on efficiency at work. It focuses on one aspect of optimism, i.e. the way positive events are interpreted by sales and related workers. The aim of the work, in addition to presenting the theoretical aspects of optimism, is checking whether there is any relationship between different dimensions of optimism, such as the range, stability and personalization of positive events and the workers’ efficiency. Material and Methods: The article was prepared on the basis of the results of the research project carried out under the Research Fund of Pope John Paul II State School of Higher Education in Biała Podlaska. The study bases on the concept of optimism devised by M. Seligman. Results: The research results suggest that there is a connection between the level of efficiency and optimism. In turn, no connection between the way successful events are personalized and the level of employees’ efficiency was found. Conclusions: Studies allow to draw some general conclusions about the existing connection between the level of optimism and effectiveness at work, which opens further research opportunities in this area. The survey results may also have a practical application. By introducing workers to elements of psychological therapy, the employer may affect their level of optimism and, consequently, their effectiveness at work.