Quantum dynamical calculations on ArI2 photodissociation have been performed using ab initio and semi-empirical potential energy surfaces, which support both linear and T-shaped isomers in the ground electronic state. Whereas the photon absorption spectra for the T-shaped isomer consist of narrow and intense bands, those for the linear isomer result from the superposition of a continuous background and peaks due to linear quasi-bound states. Vibrational distributions for the linear isomer are broader than those originating from the T-shaped one. Rotational distributions for the linear isomer are smooth and characteristic of a fast dissociation dynamics, whereas those for the T-shaped isomer are highly oscillatory. Implications of these results on the interpretation of experimental data are discussed.