A new type of photoinduced nitric oxide (NO) donors was designed from nitrobenzene derivatives. Visible-light irradiation of 2,6-dimethylnitrobenzenes bearing extended pi-electron systems at the 4-position revealed efficient NO release using ESR analysis and the Griess assay. Computational study and ultraviolet spectrum analysis suggested that the NO-releasing activity was closely related to the conformation of the nitro group, the absorption intensity, and the length of the conjugated pi-electron system. Employing the photodependent cytotoxicity of compound 14 against HCT116 human colon cancer cells, it was demonstrated that 4-substituted-2,6-dimethylnitrobenzene analogues are useful NO donors for the time- and site-controlled NO treatment.