Purpose The planar average equilibrium dose Deq (in air kerma terms) is a new CT dose index which is analogous to the CTDIvol, but considers the contribution of radiation scattered beyond the 100-mm range of integration along z [1] . The purpose of this work was to measure Deq in Abd/Pelvis and Chest scans using the Optima CT660 System for medium adult patient [2] and to compare them with the corresponding CTDIvol. Methods The measurements were performed in agreement with the AAPM Task Group 111 Report [1] , i.e. by using a small volume ionization chamber (Farmer-type) positioned in a phantom long enough to establish dose equilibrium at the location of the chamber. The cumulative exposure for different z-scan lengths (L), were recorded at the longitudinal centre of the central and peripheral axes of the phantom. An inter-calibration procedure, which uses the same CT beam of the scans and a pencil type ionization chamber, was implemented to obtain an adequate N K calibration factor. To perform the scans of reference, we chose the Abd/Pelvis CT Protocol [2] for Optima CT6602. The uncertainty of measurements was assessed following the GUM [3] recommendations. Results The Figures show the cumulative dose at z = 0 vs L for the central (red curves) and peripheral axes (blue curves) for different tube currents. The (Deq vs. CTDIvol) in mGy units were; (17.1 vs 13.5) for the Abd/Pelvis scans and (6.4 vs 5.1) for the Chest scans. Conclusions CTDIvol underestimates the dose by aprox. 27%, CI (25, 29) at P(68%).