The molecular structures of N-(2-hydroxyethyl)-3,5-dinitrosalicylaldimine and N-N'-bis(acetophenylketimine)-1,4-diaminobuthane were determined using X-ray diffraction. It was established using the difference Fourier map that the phenolic hydrogens were situated on the iminic nitrogen. Identical observations of the molecular structure were made for similar Schiff bases in literature, and it was established that this situation was not in agreement with the IR and NMR results. The molecular structure of N-(4-hydroxylphenyl)-benzaldimine was determined using X-ray diffraction for comparison. Similar compounds were prepared and their FTIR spectra were investigated.