Confocal microscopy is introduced as a new and generally applicable method for the characterization of the vertically-aligned carbon nanotubes (VACNT) forest height. With this technique process control is significantly intensified. The topography of the substrate and VACNT can be mapped with a height resolution down to 15 nm. The advantages of confocal microscopy, compared to scanning electron microscopy (SEM), are demonstrated by investigating the growth kinetics of VACNT using Al ₂ O ₃ buffer layers with varying thicknesses. A process optimization using confocal microscopy for fast VACNT forest height evaluation is presented.