The photochromic behaviour of 1-(2-naphthoxy)anthraquinone (1) was investigated using electronic spectroscopy and kinetic analysis of the decay of coloured species. The decay of coloured species well obeyed first-order kinetics and consisted of two processes, reversion to the starting substance and the change toward final formation of 1-hydroxyanthraquinone (2). The reversion process was revealed to proceed through two different pathways having activation enthalpies of 30.5 and 104 kJ mol-1. The lower value suggests that the reversion proceeds from a rotational isomer of 1 while the higher value comes from a structural isomer of 1, 9-naphthoxy-1,10-anthraquinone. The activation enthalpy of the change toward final formation of 2 was 49.1 kJ mol(-1). The possible formation of the two different coloured species from the two conformers of 1 on light irradiation was discussed.