This work investigate electromagnetic and thermal properties of poly(lactic) acid-based composites with graphene nanoplates (GNP) and multiwalled carbon nanotubes (MWCNTs), produced by solution blending method. It was found that the MWCNT carbon nanotubes are an effective filler for both absorption and reflection of electromagnetic waves in the GHz and THz frequency domains. The higher aspect ratio of carbon nanotubes, compared to industrial MWCNT, is the cause of better electromagnetic characteristics of nanocomposites prepared by solution blending method (SB). The DSC analysis of the samples shows that the glass transition is around 60oC, followed by cold crystallization with enthalpy and melting temperature around 150oC. The TGA analysis show, that the thermal stability of PLA polymer is improved by addition of 6% MWCNTs and GNP.