Nanoparticles have a high potential for use in medicine and pharmacy, especially as nanodelivery systems used in anti-cancer therapy. Their advantage is protection, stabilization and selective delivery of a compound to a target site. Although, potential toxicity of nanoparticles need to be evaluated before their use. The goal of our master thesis was to investigate potential toxic effect of poly-epsilon-caprolactone (PCL) nanoparticles coated with poly-glutamic acid (PGA), poly-(lactic-co-glycolic) acid (PLGA) with encapsulated selenium (Se) nanoparticles and selenium (Se) nanoparticles coated with bovine serum albumin (BSA). After exposure to solutions of tested nanoparticles we evaluated their cytotoxicity with MTT assay, reactive oxygen species (ROS) production and subsequent oxidative stress with DCFH-DA assay and genotoxic effects of nanoparticles with Comet assay. Our results showed no biologically relevant toxic effects on human hepatoma (HepG2) cell line in all tested samples of nanoparticles although slightly increased ROS production and DNA strand breaks was detected in cells, which were exposed to ND PCL without PGA.