This work describes results of investigations relative to composition and structure of the initial products of the addition of oxiranes to melamine analyzed by H-1-NMR spectrometry. The work Algebraic equations are shown that describe changes of contents in the functional groups of intermediate products in the function of the number of moles of oxirane that were attached. Reactivity of individual function groups of intermediate products are also discussed. The structure of polyetherols with an s-triazine ring that forms in the reaction of melamine with oxiranes is proposed on the basis of these investigations.