New trends in research are finding materials who would compete in open market with it's properties, biodegradability and production from renewable sources of energy. Polylactide is one of those materials, and with addition of carbon nanotubes it can compete in the open market. In this study the addition of different quantities of modified carbon nanotubes (MWCNT-COOH; MWCNT-COOC12H25) in PLA was investigated. Samples were prepared by melt mixing in a Brabender plasticoder. Within this study morphology, mechanical properties and mechanism of failure with scanning electron microscopy (SEM) and universal mechanical testing machine were investigated. Thermal properties were investigated by differential scanning analysis and thermal stability was determined by thermogravimetric analysis. Electrical properties were investigated by measuring resistance using four probe method. Results showed the most significant increase of mechanical properties for PLA systems with MWCNT-COOH and MWCNT-COOC12H25 nanofillers up to 2 % wt. PLA nanocomposites (up to 2 % wt) with carbon nanotubes functionalized with long alkyl chains (PLA/MWCNT-COOC12H25) have slightly better properties than systems with MWCNT-COOH due to better distribution of MWCNT-COOC12H25 in PLA matrix, which is confirmed also by fracture surface analysis. DSC results indicate that addition of both fillers accelerates nonisothermal crystallization of PLA matrix and this effect is more pronounced up to 2 % wt. Addition of MWCNT-COOC12H25 nanofiller, due to long alkyl chains that entrance in a matrix, more significantly hinders ordering of polymer chains in the crystalline form. Regardless of the type of grafted functional groups on the surface of MWCNTs, during the cold crystallization a higher proportion of lower-ordered structures than in a pure PLA matrix were created. The most prominent improvement of thermal stability is obtained by the addition of 2% wt of fillers. These results can be attributed to formation of barrier that carbon nanotubes formed and to the very high thermal conductivity of MWCNTs. Depending on the type of functional groups on the carbon nanotubes difference in the improvement of the thermal stability were not observed. The results of electrical conductivity show significant improvement of conductivity with addition of small amounts of functionalized MWCNTs up to 0.5% wt due to the formation of three-dimensional conductive network in the PLA matrix. The investigated nanocomposites have potential use for electrostatic painting and dissipation of electrostatic charge.