The present study analyzed the Italian scenario of OHSAS 18001 certified companies. In particular, the aim of this work is to investigate the relationships between four factors that companies have to consider during BS OHSAS 18001 implementation: the decisional factors which influence the company's choice to adopt certification, the success and failure factors, responsible for successful or unsuccessful OHSAS-18001 implementation and the company's improvement. A thorough literature review concerning OHSAS-18001 and Health, Safety and Environment (HSE) Systems was conducted in order to identify the main factors that have an impact on OHSAS 18001 implementation. The researchers studied the relationships between these factors and a structural equation modeling (SEM) approach was employed to test the hypothesized model. Results indicate that the factors that push Italian companies to adopt certification have a positive correlation with the success factors necessary for the implementation of the OHSAS-18001 standard. This means that decisional factors are fundamental for successful implementation and for company improvement. Moreover, decisional factors also have a strong influence on enterprise improvement. In fact certification is seen as a prerequisite for survival in the current market, allowing insurance benefits, a greater control of potential risks and a reduction in staff injuries. However a remarkable increase in bureaucracy, a lack of specialized personnel and high certification costs have been identified as the main failure factors in unsuccessful BS OHSAS 18001 implementation. This research study also highlights the interest of companies in reducing their social responsibility by implementing the OHSAS 18001 standard. In conclusion this study has an important role in describing the current Italian scenario, providing interesting information for both researchers and practitioners since it defines the main enabling factors for successful BS OHSAS 18001 implementation and the main problems that practitioners could face. (C) 2016 Elsevier Ltd. All rights reserved.