Abstract: The series of eight substituted amides of 5-hydroxy-2-methylquinoline-7-carboxylic acid were prepared. The synthetic procedures of the compounds are presented. All the prepared quinoline derivatives were analyzed using RP-HPLC method for the lipophilicity measurement and their lipophilicity was determined. The prepared compounds were tested for their photosynthesis-inhibiting activity (the inhibition of photosynthetic electron transport in spinach chloroplasts (Spinacia oleracea L.) and the reduction of chlorophyll content in (Chlorella vulgaris Beij.). Several compounds showed the biological activity comparable with or higher than the standard 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). The relationships between the lipophilicity and the chemical structure of the studied compounds are discussed as well as the structure-activity relationships (SAR) between the chemical structure and the biological activities of the evaluated compounds.