Background. Scar-related atrial tachycardias (ATs) are very challenging and no comparative studies have been conducted between the up-to-date systems, namely the new Confidense HD coloring mapping module (HD) and the new Rhythmia (RM) mapping system. Objectives. Our study sought to compare both strategies in terms of: (1) diagnosis and immediate treatment success: (2) procedure parameters in AT presenting patients. Methods and Results. Overall, 38 patients (68±9 years old) were randomized (HD=20, RM=18). The AT mechanisms did not differ between the groups: macro/small loop reentrant mechanisms were more common in both groups (12/20 [60%] versus 10/18 [56%], P=0.9), with the remaining diagnosed as multiloop (5/20 [25%] versus 4/18 [22%]; p=0.9); focal (1/20 [5%] versus 2/18 [11%], P=0.9), and localized reentrant (2/20 [10%] versus 2/18 [11%]). The procedure parameters were as follows: tachycardia cycle length (275±30 vs. 280±50; p=0.7); number of activation maps per patient (2±1 vs 2±1; p=0.9); procedure time (138±90 vs. 139±90 min; p=0.98); X-ray time exposure (20±11 vs. 24±18 min; p=0.42); RF application time (39±36 vs. 25±28 min; p=0.21); and mean number of circuits per patient (1.8±1 vs. 1.6±0.9; 0.6). Acute success was obtained in 15/20 pts (75%) of the HD group and 14/18 (78%) of the RM group (p=0.9). The procedure failed in 2 patients with the HD coloring and they were converted to the RM group without success. No crossover was carried out in the RM group. Conclusions. This randomized study demonstrates that HD coloring and Rhythmia systems exhibit a similar efficacy in achieving acute AT termination.