The printing and nonprinting surfaces on a lithography printing plate are in the same level and the difference between them is achieved through opposite physical-chemical properties. The printing surfaces are oleophilic (hydrophobic) and in the printing process they attract oily based printing ink and the nonprinting surfaces are hydrophilic which enables them to adsorb fountain solution in the printing process. The conventional printing plate making process consists mainly of following major processes: exposure of the photoactive coating through fi lm, developing process in developing solution and washing out. Diazo positive printing plates were used in this research. The diazo positive photoactive coating becomes soluble in alkaline solution by exposure. Samples prepared for this research are all exposed and developed in the same time but are developed in solution with different molar concentration of potassium alkali. Molar concentrations used were 0,2 moldm-3, 0,4 moldm-3, 0,5 moldm-3, 0,6 moldm-3, 0,8 moldm-3, 1 moldm-3 i 1,5 moldm-3. Characterization of printing and nonprinting areas of the printing plate was made on prepared samples. The measurements of the coverage values of printing areas and of the contact angle between nonprinting areas and fountain solution were performed. The results obtained by this research have showed that molar concentration of alkali in a developing solution has signifi cant infl uence on characteristics of printing as well as nonprinting areas. If the molar concentration of alkali in solution is to high, dissolving of whole photoactive coating will occur which makes printing plate useless for exploitation. The nonprinting areas are also damaged when developing in solution with high molar concentration alkali solution. When the molar concentration of alkali in solution is to low some parts of photoactive coating remains on nonprinting areas which disables adsorption of the fountain solution on those areas. Obtained results indicate that it is essential to monitor chemical composition of developing solution to determine parameters of the developing process. To obtain best possible printing plate quality one must keep results of this research in mind and use optimal process requirements.