The paper compares the visible wavelengths excited resonance Raman and the near-infrared Fourier transform (NIR-FTR) Raman spectroscopy methods in terms of their convenience and informativeness for studies of diacetylenes (DA) and polydiacetylenes (PDA). It is shown that the combination of excellent precision with the reliability of measurements on the samples which are essentially transparent to both the exciting laser wavelength, 1064 nm, and the NIR-Raman photons makes NIR-FTR spectroscopy an ideal tool for quantitative measurements of the solid-state structural transformations in PDAs. In particular, thermally induced polymerization of a model DA, PTS has been reinvestigated in situ by the NIR-FTR method. The data so obtained suggest occurrence of a sharp but continuous and concerted structural transition during the polymerization of PTS. Other peculiarities, namely the apparent lack of both the intensity and frequency dispersions with the polymer π-conjugated length in the NIR-FTR spectra, as well as a non-trivial reasonant enhancement of the latter are noted.