Spin-dependent structure functions of the photon

The implications of the positivity constraint on the presently unknown polarized structure function of the photon, g1γ(x,Q2), are studied in detail. In particular the non-trivial consequences of this constraint, |g1γ(x,Q2)|⩽F1γ(x,Q2), in the next-to-leading order analysis of g1γ are pointed out by employing appropriate (DIS) factorization schemes related to g1γ and F1γ (rather than to F2γ).