<p>Fifteen open-shell isomers off the forty six IPR isomers of fullerene C<sub>90</sub> were found and investigated: 5 (C<sub>s</sub>), 7 (C<sub>1</sub>), 9 (C<sub>1</sub>), 10 (C<sub>s</sub>), 11 (C<sub>1</sub>), 20 (C<sub>1</sub>), 21 (C<sub>1</sub>), 22 (C<sub>1</sub>), 23 (C<sub>2</sub>), 24 (C<sub>1</sub>), 25 (C<sub>2v</sub>), 41 (C<sub>2</sub>), 42 (C<sub>2</sub>), 43 (C<sub>2</sub>), and 44 (C<sub>2</sub>). According to developed by us approach the positions of single, double, and delocalized π-bonds in the molecules of these isomers are shown for the first time. The obtained results of electronic and geometrical structures are fully supported by DFT method with the B3LYP functional at the 6-31G and 6-31G* levels. Molecules of these open-shell isomers contain different radical substructures (mainly the phenalenyl-radical substructures), they should be unstable and could not be obtained as empty molecules. Nevertheless, there is a possibility of obtaining them in polymeric forms or as endohedral or exohedral derivatives.</p
