This paper explains the concept of treasury shares, legal regulation and the reasons why there is a special legal regime for treasury shares. Treasury shares represent a special category within commercial law. Treasury shares are shares that, after being issued, are acquired by the joint-stock company that issued them. Due to the importance of treasury shares in large companies, their acquisition and holding is associated with numerous legal restrictions and special rules. Such shares are specially regulated by law due to the importance of two principles of share law: the principle of capital contribution and the principle of capital preservation. Treasury shares do not confer any rights during the time they are held by the company itself, and these rights are activated again when other persons acquire them. If during that time the rights from the shares would not rest, the right to vote and the right to challenge the decision of the general assembly would be held by the management, which would disrupt the relationship between the management and the general assembly. The law prescribes two ways of acquiring treasury shares: on the basis of a decision of the general assembly or without a decision of the general assembly, but only if there is one of the reasons listed in regulations. The acquisition of treasury shares can be motivated by preventing unacceptable and hostile takeovers on the capital market, enabling the realization of existing rights to purchase or conversion into ordinary shares, realizing business mergers and acquisitions, preventing further decline in their value on the market, etc. The law prescribes the assumptions that must be met in order for a joint-stock company to acquire its treasury shares. Therefore, the violation of these legally prescribed assumptions leads to the illegal acquisition of shares and to certain consequences for the company. However, if the company acquires its treasury shares in accordance with the law, without violating the legal provisions, there is no legal limit on how long it can hold them, that is, the company may hold them for as long as the management decides.