Ahmed El-Beialy¹, Shaza Abd El-Nabi², Ahmed Fouda³ and Marwa Shamaa^{4 1}Professor of Orthodontics, Faculty of Dentistry, Mansoura University, Egypt. ²Assistant Professor of Orthodontics, Faculty of Dentistry, Mansoura University, Egypt. ³Lecturer of Orthodontics, Faculty of Dentistry, Mansoura University, Egypt. ⁴Assistant Lecturer of Orthodontics, Faculty of Dentistry, Mansoura University, Egypt. Abstract: Objectives: Spiral CT has the potential to overcome the limitations of standard transmission radiography and current CT based methods. Methods: The objective of this study was to compare the standard plaster models taken using alginate impression material with their digital counterparts prepared by scanning the patients with a spiral CT (Light speed Pro, General Electric medical CT scan machine, Wakesha, Wis). Results: On the basis of the results of the present study, the following could be detected: excellent agreement between both models as proved by the absence of significant difference and the significantly excellent agreement and association between the two modalities for the different measurements: mesiodistal width of the maxillary and mandibular teeth, and the different arches measurements like: maxillary and arch perimeters; arch lengths; arch widths and the mandibular intercanine width. Conclusions: In conclusion; digital models are acceptable replacement for plaster casts for the routine measurements made in most orthodontic practices. Keywords:Digital Models, Spiral CT, Standard Cast Models.