play an essential role in determining the structure of biological systems. The acetamide molecule is the simplest model of such system. Amides and their water clusters have been extensively studied experimentally by various methods. However, quantum chemical calculations allow us to obtain and to analyze in detail structural and energetic characteristics of the acetamide-water complexes. It allows improving the understanding of how these groups can interact with each other and with the solvent molecules surrounding them. Besides, it allows obtaining important microstructural information which is not available from any physical experiment. We have investigated the structure of acetamide complexes with various numbers of water molecules (1-4 molecules) forming different types of hydrogen bonds. Ab initio molecular calculations were performed using the Gaussian 09 program package. Optimization of geometric parameters and NBO analysis were performed in the framework of density functional theory (DFT) with B3LYP hybrid functional using the aug-CC-pVTZ basis set. The initial configurations of the complexes were created in the GaussView program by using optimized molecular structures. Each obtained structure corresponds to the global minimum on the potential energy surface. Taking into account the basis superposition error (BSSE), we calculated distances and angles characterizing a hydrogen bond and the intermolecular interaction of the studied systems. Stabilization energy of the hydrogen bonds and the magnitude of charge transfer, the shifts of vibrational frequencies relative to vibrational frequencies of the isolated molecules and the energy of hydrogen bonds obtained in the framework NBO analysis. It is possible to form two types of hydrogen bonds X-H ··· Y, where the molecule of acetamide can be either a donor or an acceptor of the proton. Based on the geometric and energetic criteria, it was found that the bond between the C = O ··· H-O, as well as the N-H ··· O bond, refers to the bonds of medium strength. The formation of bonds is also confirmed by the presence of critical points in all complexes on H ... Y bonds obtained by the QTAIM method using the AIMAll package. Thus, it was established that the water molecule is much stronger interacts with the carbonyl oxygen atom than a proton of the amino group. The most stable complex with two H-bonds, i.e. the case when the water molecule is connected with the O=C-group of the acetamide, but is located nearby the NH2-group and also interacts with it. However, a comparison of the geometric parameters of the complexes showed that these bonds are distorted.