The new and fast scatterometry method called optical diffraction microscopy is compared with atomic-force microscopy by use of cross-section scanning-electron microscope images as references. The sample is a high-aspect-ratio grating with a period of \approx 1000\text{\hspace{0.17em} nm} . To allow the atomic-force microscope to track all parts of the grating profile, the grating is investigated at different tilt angles. The measured quantities of the profile include sidewall angle \gamma \hspace{0.17em}\left(\approx 90°\right) , groove height h\left(\approx 2000\text{\hspace{0.17em} nm}\right) , and degree of filling f\left(\approx 40\%\right) . The two methods, which respond to quite different material properties, give consistent results within standard uncertainties of u\left(\gamma \right)\le 0.8° , u\left(h\right)\le 15\text{\hspace{0.17em} nm} , and u\left(f\right)\le 1\% .