An x-ray diffraction structural study was carried out on dicyanoglyoxime trihydrate (DCG) and dimesitylglyoxime (DMG) on an automatic diffractometer using MoK radiation using 851 reflections, R=0.031 (DCG) and 862 reflections, R=0.030 (DMG). The unit cell parameters of the monoclinic crystals of DCG, C₄H₂N₄O₂·3H₂O at –155°C are as follows: a=17.34(1), b=8.395(6), c=6.280(5) Å, =97.23(6)°, Z=4, space group C2/c. The unit cell parameters of the monoclinic crystals of DMG, C₂₀H₂₄N₂O₂ at 23°C are as follows: a=12.734(2), b=8.885(2), c=16.087(2) Å, =101.31(1)°, Z=4, space group I2/a. DCG and DMG molecules in the crystal have anti form with anti-peri-planar orientation of the oxime groups. The planar dioxime fragments features -conjugation of the oxime groups. The molecules in the crystal are connected by hydrogen bonds, which form a three-dimensional framework in the structure of DCG and chains along the a-axis in the structure of DMG.