In the past few years, and in a number of countries, there has been a noticeable increase in the number of organizations withdrawing from the Quality Management System standard iso 9001. Hence the need to analyze this phenomenon of decertification and to explain not only the extent to which it is taking place but also why companies are taking such decision. This study analyzes the reasons for withdrawing from iso 9001 using data obtained from quality managers at 130 Polish organizations which opted out of certification in 2012 and 2013. The data shows that the most important reasons for withdrawal were related to internal factors, such as financial problems within the organizations, a perceived lack of added value from certification, and organizational changes (such as internal restructuring). There were also external factors: customer-driven reasons for the decision to withdraw were also given. Using this data we provide a classification of the reasons for decertification, which can shed light on the effectiveness of activities related to qms implementation, certification and cancellation. We believe this will be of interest to managers of organizations and certification bodies, as well as researchers. The paper provides the potential basis for a quality management strategy directed towards identifying and dealing with the costs and problems that iso 9001 can generate for companies.