Two fundamental pathways can be distinguished acting in light sensitive formulations containing IR dyes: (1) transformation of the incident IR energy into heat followed by several thermal processes; (2) interaction between excited states of the IR dye and the ground state of another compound leading to reactive intermediates, which then react with other components to final products. Based on general accepted theories of excited state chemistry, estimations and conclusions for both pathways will be made for systems containing IR dyes. As follows, electron transfer reactions can be compete successfully with the fast physical deactivation processes of excited dye molecules. Some results for such reactions will be presented.