In this study a series of nine 3-hydroxynaphthalene-2-carboxanilides, disubstituted on the anilide ring by fluorine, chlorine and bromine in various positions, was prepared by microwave-assisted synthesis and characterized. The compounds were tested for their activity related to the inhibition of photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. The PET-inhibiting activity of the compounds was within a wide range, but rather moderate; the highest activity within the series of the compounds was observed for N-(3,5-difluorophenyl)-3-hydroxynaphthalene-2-carboxamide. The compounds were found to inhibit PET in photosystem II.