This paper analyzes the exercise of powers and duties which co-owners have regarding to common parts of property and their mutual relations with regard to the sam. The aim of this paper is to approximate and clarify the concepts related to the mutual relations of co-owners of property and ways of exercising their powers and duties with respect to the whole condominium. The purpose of this paper is to provide, with the help of legal regulations and case law, a more detaild insight into the problem of exercising the powers and duties regarding the whole property and to point out possible solutions to them. The first part of the paper explains the term of condominium, gives a historical overview, reasons for the formation, features and establishment of condominium. Special attention was paid to the powes and duties of the co-owners and in this context the chapter related to regular and extraordinary affairs, other powers that co-owners have regarding the whole property, the cost of the whole property, joint reserve, the manager, inter-ownership agreement, the duty to report damages, urgent and necessary repairs were discussed. The last section presents comparative experiences of other countries in managing apartment buildings, as well as possible solutions to the problem of managing apartmet buildings in the Republic of Croatia.