Six representative isotope-labeled samples of titanium dioxide were synthesized: Ti¹⁶O₂, Ti¹⁷O₂ and Ti¹⁸O₂, each in anatase and rutile forms. Their Raman scattering was analyzed at temperatures down to 5 K. Spectral assignment was supported by numerical simulation using DFT calculations. The combination of experimental and theoretical Raman frequencies with the corresponding isotopic shifts allowed us to address various still-open questions about the second-order Raman scattering in rutile, and the analysis of overlapping features in the anatase spectrum.