Some of isonicotinic acid hydrazide derivatives are widely used in medical practice, as TB, antimicrobial, antifungal, anticancer drugs. The biological activity of these compounds correspond well to their structure. In this connection, the accumulation and systematization of experimental data related to the structure of new isonicotinic acid hydrazide derivatives is the current trends in modern chemistry. Therefore the aim of this study was to investigate the structure of 2- and 3- formylpyridines isonicotinoyl hydrazones by X-ray methods. The molecules of I and II are non-planar; the mean square planes of its terminal pyridine cycles are oriented at the angles of 23.3, 6.7 and 4.6, 6.7 with respect to the planar fragment of the isonicotinoyl hydrazones. In the crystal I forms the one-dimensional hydrogen-bonded infinite chains along b axis while compounds of II are self-assembled into 3d hydrogen bonded network.