The differential cross section for the process γγ→ηπ0 has been measured in the kinematic range 0.84 GeV<W<4.0 GeV, |cosθ*|<0.8, where W and θ* are the energy and π0 (or η) scattering angle, respectively, in the γγ center-of-mass system. The results are based on a 223 fb−1 data sample collected with the Belle detector at the KEKB e+e− collider. Clear peaks due to the a0(980) and a2(1320) are visible. The differential cross sections are fitted in the energy region 0.9 GeV<W<1.46 GeV to obtain the parameters of the a0(980). Its mass, width and ΓγγB(ηπ0) are measured to be 982.3−0.7−4.7+0.6+3.1 MeV/c2, 75.6±1.6−10.0+17.4 MeV and 128−2−43+3+502 eV, respectively. The energy and angular dependences above 3.1 GeV are compared with those measured in the π0π0 channel. The integrated cross section over |cosθ*|<0.8 has a W−n dependence with n=10.5±1.2±0.5, which is slightly larger than that for π0π0. The differential cross sections show a sin−4θ* dependence similar to γγ→π0π0. The measured cross section ratio, σ(ηπ0)/σ(π0π0)=0.48±0.05±0.04, is consistent with a QCD-based prediction.9 MoreReceived 8 June 2009DOI:https://doi.org/10.1103/PhysRevD.80.032001©2009 American Physical Society