The continuous increase in the usage of pesticides in modern agriculture is becoming inevitable due to more efficient food production and the increase in world population. On the other hand, harmful effects of pesticides on humans and other organisms (domestic animals, beneficial insects, bees, birds, fish, etc.) cause concerns of public institutions due to their bio accumulation effect on the soil and aquatic ecosystems. Therefore, in this paper, the photolytic and photocatalytic degradation with photocatalysts titanium dioxide (TiO2) and nanocomposite of titanium dioxide and carbon nanotubes (TiO2/CNT) of imidacloprid in a pilot reactor with compound parabolic mirrors (CPC) was analysed. According to the kinetics of the pseudo first-order degradation, the apparent rate constants of the photolytic degradation of imidacloprid (k=0.0058 min-1) and the photocatalytic degradation of imidacloprid with TiO2 (k=0.0058 min-1) and with TiO2/CNT (k=0.00934 min-1) were determined. Faster degradation (3.6 hours) of imidacloprid can be achieved using TiO2/CNT photocatalyst in comparison to the usage of TiO2. The analysis of the degradation products revealed three (m/z=212.0585; m/z=209.0589 and m/z= 211.0745) out of the four most common photolytic degradation by-products of imidacloprid, while only one degradation compound (m/z = 274.0518) of imidacloprid was determined during photocatalytic degradation on TiO2 and TiO2/CNT photocatalysts. It indicates the need for a more detailed analysis since the experiments were carried out under the actual conditions of solar radiation.