In this paper, we present a combined STM and EPR study on the adsorption and self-organization of monolayers formed from 2-(14-Carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxy (16DS) and 4',4'-Dimethylspiro(5 alpha-cholestane-3,2'-oxazolidin)-3'-yloxy (CSL) adsorbed on a highly oriented pyrolitic graphite HOPG(0001) substrate. Both 16DS and CSL molecules are persistent free radicals containing a paramagnetic doxyl group. The STM measurements of 16DS on HOPG(0001) were performed at the liquid-solid interface while the studies of CSL on HOPG(0001) were carried out under ultrahigh vacuum conditions. It was found that the 16DS molecules on the HOPG(0001) surface form a highly-ordered monolayer with a domain structure. The high-resolution STM images show structural details of 16DS molecules on HOPG(0001) revealing the paramagnetic doxyl group. In contrast, CSL molecules on HOPG(0001) form a well-ordered monolayer without domain structure. The EPR results indicate that both compounds deposited on HOPG(0001) substrate are not reduced and retain their paramagnetic character. We believe that the molecular systems described can be used in single spin detection experiments using an electron spin noise-scanning tunnelling microscopy (ESN-STM) technique. In particular, the possibility of obtaining contrast spin signals from the paramagnetic and diamagnetic parts of molecules increases the significance of our results. (C) 2009 Elsevier B.V. All rights reserved.