Recently DNA with hexadecyltrimethyl ammonium chloride (CTMA) complex has been included in some organic electronic devices. Thermal stability is one of key parameters required for successful applications in different electronic and optoelectronic devices. This work shows a possibility of enhancing thermal stability in this complexes and analyzes origin of this enhancement. Different techniques were applied to explore this issue of solid DNA-CTMA. Results of TGA analysis, DSC calorimetry, FTIR spectroscopy, and analysis of evolved gaseous products convince that chemical composition of DNA-CTMA complex remains fixed at temperatures \200-220°C. In contrast, broadband dielectric spectroscopy applied to freshly prepared thin films of DNA-CTMA revealed at 150-160°C a permanent and irreversible change of dielectric properties. This phenomenon may be attributed to a transformation affecting the microstructure. Some experiments were conducted also for the native DNA as a reference. We demonstrate that DNA-CTMA complex chemical composition is more stable at temperatures about 200°C with respect to DNA which is very important for laser operated optoelectronic applications.