It is known that the salicylaldehyde condensation products with amino alcohols in solution and in solid state may be of various tautomeric forms. The structure and physicochemical properties of these substances can also be changed by introducing various substituents in the benzene ring of salicylidene azomethine fragment. That is why it was interesting to synthesize and study the structural features of 3 - (2hydroxybenzylideneamino)-propane-1,2-diol (I) and 3 - (2-hydroxy-5-nitrobenzylideneamino) propane-1,2diol (II), which are products of condensation of salicylaldehyde and 5-nitrosalicylaldehyde with 3aminopropane-1,2-diol. The X-ray analysis data have shown that the crystals of both compounds are monoclinic, space group P21/c. Their molecules (Fig. 1 and 2.) have a similar conformation and are generally non-planar, the dihedral angle between salicylidene and amino alcohols azomethines fragments in the compound (I) is equal to 106°, and in compounds (II) 36°. In the crystal of compound (I) the molecules are combined in double layers perpendicular to the a axis. In these layers, the molecules are arranged as of “head to head”. Each individual layer consists of antiparallel chains extending along the b axis of the unit cell. The molecules in the chains are joined together through hydrogen O-H ... O bonds involving oxygen atoms of phenolic and hydroxyl groups of the molecules. The system of hydrogen bonds involving methyl and carbonyl groups and also oxygen atoms of hydroxyl groups of the molecules joins antiparallel chains of the molecules in a layer. Between adjacent layers the van der Waals interaction is performed. A special feature of the molecular compound (II) is that the alcohol OH group in amino alcohols fragments of the molecules is disordered over two positions. In the crystal of the given compound the molecules are combined into three-dimensional framework through hydrogen bonds in the formation of which one of the CH group of the benzene ring with the oxygen atom of the nitrosalicylaldehyde fragment, and also the two amino alcohols OH groups are involved.figureFig. 1. Molecular structure of compound (I). Fig. 2. Molecular structure of compound (II).In the molecules of both compounds an intramolecular N-H ... O bond is realized, with closing the second six-membered cycle. Thus, the replacement of hydrogen with the nitro-group in the salicylidene azomethine fragment leads to different molecular packing in the crystals.