Oligoester-containing semiinterpenetrating polymer networks (semi-IPNs) can be effectively used as precursors for the generation of (meso)porous networks with tunable pore sizes. In a first step, novel poly(DL-lactide) (PLA)/poly(methyl methacrylate) (PMMA)-based semi-IPNs were prepared by varying two structural parameters, namely the cross-link density of PMMA subnetwork (initial MMA/ dimethacrylate composition ranging from 99/1 to 90/10 mol %) and the cross-linker nature (bisphenol A dimethacrylate, diurethane dimethacrylate). The kinetics of the free-radical cross-linking process was monitored by real-time near-infrared spectroscopy. In a second step, the extraction of the un-cross-linked oligoester subchains from the semi-IPNs was investigated. The possibilities afforded by this straightforward and versatile route to (meso)porous polymeric materials were discussed, and the porosity of the resulting methacrylic networks was examined by scanning electron microscopy (SEM) and thermoporometry using differential scanning calorimetry (DSC). The dependence of pore sizes and pore size distributions on the cross-linker content and nature could be related to turbidity measurements of semi-IPN precursors and explained in terms of polymer-polymer miscibility through the evaluation of PLA/PMXU interaction parameters.