The paper addresses certain civil law contracts, more precisely the mandate contract, commission contract and representation contract. The commission as the basis of each representation contract represents an interrelation between the principal and the contractor, which binds the contractor to carry out certain orders for the third party. The commission as such is not exclusively related to the mandate contract. It is also a part or the basis of the commission contract and the representation contract. For each of the above mentioned contracts one can argue that there are two legal relationships: that between the principal and the contractor, i.e. the commissioner and the client on the one hand, and the giver of authorization and the assignee on the other, as well as the external relationship between the third party with whom the legal transaction is concluded and the person representing the principal. There is a difference between the specified contracts, as it is stated in the Civil Obligations Act and other references as well. The contractor acts on behalf of the principal on the basis of the mandate contract. Unlike him, the commissioner acts in his own name and on behalf of the client when operating, whereas the assignee is obligated to conclude certain legal transactions in the name and on behalf of the represented person.