In this work we present the results of an investigation about Doppler limited infrared absorbing transitions of the in-plane methyl-rocking and the asymmetric methyl deformation modes of (CD3OD)-C-13 by means of optoacoustic detection. This is an alternative and attractive technique to be applied to this methanol isotopomer, in comparison to Fourier transform spectroscopy. In fact the contamination problem associated with the fast exchange of OD by OH in the molecule limits the use of the Fourier transform technique. Using a waveguide CO2 laser of 290 MHz tunability on each line we were able to observe 20 IR absorptions, most of them of large offset. The data will be useful in theoretical analysis of this molecule, as well as in the generation of FIR laser radiation in optically pumped molecular laser.214621632