Increased need for food has resulted in intensive pesticide use. Uncontrolled use of pesticides causes their bioaccumulation in the environment, which leads to soil, air and water pollution and has a negative impact on human health. Since it is difficult to remove pesticides from water using conventional techniques and achieve strict criteria on permissible concentrations, advanced oxidation processes are used to remove pesticides from. water and wastewater, of which heterogeneous photocatalysis stands out. In this paper, the photocatalytic degradation of the neonicotinoid insecticide imidacloprid in aqueous solution was studied. The experiments were performed in an annular reactor with recirculation of the reaction mixture using an immobilized layer of TiO2 photocatalyst modified by previous exposure to UV-C radiation. The influence of the initial concentration of imidacloprid (5, 10, 15 ppm), recirculation of the reaction mixture (100, 200, 300 mL/min) and the type of applied radiation sources (UVA -8W, UVA -15W, Arcadia-8W) on the kinetic studies was investigated. The design of the experiments was prepared using the computer program Design-Expert and the course of photodegradation of imidacloprid was monitored using high performance liquid chromatography (HPLC). From the obtained experimental data, conversions were calculated and the corresponding reaction rate constants obtained according to the proposed kinetic model for the first order pseudo-reaction were estimated. The obtained experimental results showed that the initial concentration of pollutants shows the greatest influence on photocatalytic degradation. The highest conversion and the highest reaction rate constant were achieved at a pollutant concentration of 5 ppm and at a recirculation of the reaction mixture of 200 ml/min.