The topic of the master thesis is the production of emission inventory of non-road mobile machineries in the Republic of Croatia. Through the introductory part, a series of directives and amendments have been introduced, based on which the emission inventory of non-road mobile machinery has been developed. It is mentioned which emissions of harmful substances are mostly attended. Also, it will be described in several entries how the emission inventory of non-road mobile machinery should be produced and what emission inventory should contain. The steps that would be a good guide to the development of emission inventory of non-road mobile machinery will be described, which should serve as an example for the purpose of producing a high-quality register of non-road mobile machinery and facilitating the creation of an emission inventory of non-road mobile machinery. The Regulation, which has recently been adopted by the European Parliament and the Council of the European Union, on the emission of non-road mobile machinery will be presented and explained. Throughout the second part of the master thesis, categories and subcategories of non-road mobile machinery will be described. Each of the categories and subcategories of non-road mobile machinery will be added a classification number, which will facilitate the connection of non-road mobile machinery to newer data in the future. After classifying the categories of non-road mobile machinery, the process of making the register of non-road mobile machinery, method of data collection and logging will be described in detail. In addition, the problems encountered during the development of the register of non-road mobile machinery will be presented. Most importantly, the process of making the emission inventory of non-road mobile machinery together with the calculation of emission inventory of inland waterways vessels of the Republic of Croatia will be presented in detail.