This paper presents a real case story about the configuration and start-up of new Ultra Low Sulfur Diesel (ULSD) Hydrotreating units located at Petrobras' REFAP and RNEST refineries. These units design were based on a mixed virgin and cracked distillate feedstocks derived from Brazilian crudes that are typically naphthenic type with low sulfur and high nitrogen contents, high density and low cetane number in its Diesel range streams. These feedstocks features are quite particular in relation to the typical feed properties around the world. The units configuration brings an innovative approach with aromatics hydrogenation step after a very deep desulfurization section, whose goal is not only to cope with the Diesel specification according to the most restrictive Brazilian fuel regulation (10 ppm maximum sulfur content, 0.850 maximum density and 48 minimum cetane number) but also bringing additional value to the refinery by keeping the Diesel volume swell during all cycle length with no reduction in the density gain at high WABT. As expected, the innovative Diesel HDT technology is indeed leading to very good industrial results with ULSD production and improving product volume gain, consequently enhancing the refineries profit.