Introduction. Optimization of the system of central executive authorities, the implementation dates of which are set for 2018-2021, was provided by the order of the Cabinet of Ministers of Ukraine «On approval of the Concept of optimizing the system of central executive authorities» of December 27, 2017 № 1013-r. Previous processes of optimizing the system of central executive authorities took place in 2010 and 2014. Optimization is one of the forms of changes in the organization and operation of the system of central executive authorities. It has a corresponding purpose, content and features and diff ers from other forms of change («reform», «optimization», «improvement», «modernization», etc.). These terms should not be equated. However, such identifi cation is not uncommon both in the scientifi c literature and in legal acts and practice of public administration. The aim of the article. The aim of the article is to deepen the theoretical foundations of the processes of optimizing the system of central executive authorities that took place in 2010, 2014 and optimizing the system of central executive authorities, which has been going on since 2017 and until now. Results. Optimizing the system of central executive authorities is bringing it to a certain positive level of its functioning. Optimization is the achievement of the maximum allowable value of effi ciency under a stable and high-quality mode of operation of the system. Optimization is a set of measures to increase the effi ciency and eff ectiveness of activities. The terms «optimization» and «reform» are used interchangeably, as part and whole, or even identifi ed. Although each of them contains its own content. The key results of the 2010 optimization were the change of the components of the system of central executive authorities and the consolidation of relevant functions for specifi c types of central executive authorities. The optimization of the system of central executive authorities in 2014 was actually reduced to the formation, liquidation and reorganization of a number of central executive authorities, as well as the assignment of additional functions to certain ministries. Unfortunately, the optimization of the central executive system, which has been going on since 2017, is lagging behind the planned deadlines, in many ministries it is being carried out formally, or it does not meet the goal to be changed. As a result, there is a threat to increase the effi ciency and eff ectiveness of the organization and operation of the system of central executive authorities. Existing terminological inconsistencies and arbitrary choice of form for changes required by the central executive system may be among the reasons for not achieving the expected result of such changes. As well as the processes of optimization, reform of the system of central executive authorities should be preceded by the preparation of a conceptual document that defi nes their purpose, criteria, content, stages and deadlines. Conclusions. The changes required by the system of central executive authorities in the relevant periods of its development must correspond to a certain form of change with its own characteristics (optimization, reform, improvement, modernization, etc.). Changes in the organization and operation of the central executive system in 2010 and current changes are more in line with the form of «reform» of the central executive system than «optimization». The purpose of these processes in diff erent years coincided and was to achieve positive changes in the organization and operation of the system of central executive authorities. The content of the changes and its scope were diff erent – comprehensive changes in 2010 in the organization of the system of central executive authorities and the functions performed by central executive authorities; smaller-scale changes in 2014; strengthening the role of ministries in shaping public policy and depriving them of their inappropriate powers from 2017 to the present. The results of changes in the organization and operation of the central executive system in 2010 in terms of the new species classifi cation of central executive authorities and their functions justify themselves in practice and can be used as basic data to improve the central executive system in modern times. Key words: system of central executive authorities, optimization, reforming, improvement, effi ciency, eff ectiveness.