In the article, the results of the research on reactivity of natural organic matter in regard to disinfection by-products, specifically trihalomethanes (THM) formation, with the use of model waters, are discussed. Additionally, the evaluation of different processes used in water treatment, i.e. photocatalysis, MIEX®DOC and membrane processes, is made. It was found that the affinity of particular natural organic matter compounds to form chlorination by-products could be arranged in a series: hydrophobic fraction (HA) > hydrophilic fraction (FA). The applied treatment processes efficiently decreased the concentration of disinfection by-products (DBPs) precursors and characterized with different removal mechanisms. Water treated by means of photocatalysis (specific potential of ∑THM was 30 μg/mg dissolved organic carbon (DOC) for HA and 12 μg/mg DOC for FA) revealed lower affinity to form chlorination by-products in comparison with water undergone to MIEX®DOC process (specific potential of ∑THM was 38 μg/mg DOC for HA and 29 μg/mg DOC for FA). Moreover, combination of those methods with membrane processes efficiently reduced DBPs formation potential. In nanofiltration effluents DBPs potential were very low and equalled to 50 μg/L for HA and 15 μg/L for FA.