Conventional histological validation is a generally accepted gold standard in dental caries studies [1]. Besides demanding complex laboratory processing, about 80% of the tooth material is lost irreversibly by sectioning and polishing. Conventional radiography and X-ray Micro Computed Tomography (XMT) have previously been investigated as non-destructive alternative techniques [2,3]. XMT is a high-resolution imaging technique, not requiring elaborate specimen preparation. Today's commercial desktop XMT systems significantly reduced the cost and complexity of the technique. The aim of the present study is to compare XMT imaging and histological sectioning for categorical caries gradation and assessment of lesion depth and size.