Author Institution:The methods which have been derived especially for analysing complicated vibration-rotation high resolution spectra of different type polyatomic molecules are discussed. The efficiencies of those are methods are illustrated by the results of the first studies of some excited strongly interacting vibrational states of the CH2βD2β,H2βSe,D2βS,HDS, and some other polyatomic molecules. Possibility of using of obtained information in the problem of determination of fundamental molecular parameters is discussed