The crystal structures of several compounds obtained from recently synthesised α-amido-α-aminonitrones were determined by X-ray diffraction. The compounds belonged to three different classes: 1,2,5-oxadiazin-4-ones, amidines and dibenzo[d,f][1,3]diazepines. In spite of the fact that they were yielded in reactions of various kinds, all the products contained the same amido-amidine moiety. We discovered that some geometrical parameters within the moiety had non-typical values; for example the C_sp²–C_sp² single bonds were outstandingly long. A detailed analysis of the products' geometry, aided by DFT calculations for selected structures, allowed us to propose mechanisms of their formation.