Efficiency of analysis using generalized estimation equations is enhanced when intracluster correlation structure is accurately modeled. We compare two existing criteria (a quasi-likelihood information criterion, and the Rotnitzky–Jewell criterion) to identify the true correlation structure via simulations with Gaus-sian or binomial response, covariates varying at cluster or ob-servation level, and exchangeable or AR(1) intracluster correla-tion structure. Rotnitzky and Jewell's approach performs better when the true intracluster correlation structure is exchangeable, while the quasi-likelihood criteria performs better for an AR(1) structure.