4-Membered heterocycles offer exciting potential as small polar motifs in medicinal chemistry but require further methods for incorporation. Photoredox catalysis is a powerful method for the mild generation of alkyl radicals for C–C bond for-mation. The effect of ring strain on radical reactivity is not well understood, with no studies that address this question sys-tematically. Examples of reactions that involve benzylic radicals are rare, and their reactivity is challenging to harness. This work develops a radical functionalization of benzylic oxetanes and azetidines using visible light photoredox catalysis to prepare 3-aryl-3-alkyl substituted derivatives and assesses the influence of ring strain and heterosubstitution on the reactivity of small-ring radicals. 3-Aryl-3-carboxylic acid oxetanes and azetidines are suitable precursors to tertiary benzylic ox-etane/azetidine radicals which undergo conjugate addition into activated alkenes. We compare the reactivity of oxetane radi-cals to other benzylic systems. Computational studies indicate that Giese additions of unstrained benzylic radicals into acry-lates are reversible and result in low yields and radical dimerization. Benzylic radicals as part of a strained ring, however, are less stable and more 𝜋-delocalized, decreasing dimer and increasing Giese product formation. Oxetanes show high product yields due to ring strain and Bent’s rule rendering the Giese addition irreversible.