The influence of the surface morphology of semicrystalline polyamide 12 PA12! on the adhesion of thin silicon oxide coatings is analyzed by means of uniaxial fragmentation tests and scanning local-acceleration microscopy SLAM!. Two types of PA12 substrates are investigated, namely, as-received PA12, which contains large spherulites, and quenched PA12, which has a relatively smooth, homogeneous surface structure. The adhesion of the coating is found to be identical for the two types of PA12. This indicates that plasma deposition of the oxide leads to an equivalent functionalization of the two types of surfaces. Nonetheless, localized delamination is observed at spherulite boundaries, and is argued to result from strain concentrations in the corresponding soft zones, revealed by SLAM measurements.