Three new series of tricyclic pyridazinones have been synthesized and tested in vitro in order to assess (i) their ability to inhibit aldose reductase enzyme (ALR2) and (ii) their specificity toward the target enzyme with respect to other related oxidoreductases, such as aldehyde reductase, sorbitol dehydrogenase, and glutathione reductase. The inhibitory capability of the most effective compounds (IC50 values ranging from 6.44 to 12.6 microM) appears to be associated with a rather significant specificity for ALR2. Molecular mechanics and molecular dynamic calculations performed on the ALR2-inhibitor complex give indications of specific interaction sites responsible for the binding, thus providing information for the design of new inhibitors with improved affinity for the enzyme.