Abstract Background The paced QRS duration (pQRS) is associated with the risk of developing a pacing-induced cardiomyopathy. His bundle pacing (HBP), either selective (sHBP) or non-selective (nsHBP) can achieve a rather narrow pQRSd in patients with a narrow intrinsic QRS (iQRS) or right bundle branch block (RBBB). We prospectively analyzed the pQRS in sHBP and nsHBP and correlated it with the iQRS. Patients and Methods All consecutive patients who received an implantation with sHBP or nsHBP were enrolled and received a 12-lead ECG before and after implantation (digital recording, 25 mm/s). Measurements of the pQRS after implantation were performed in unipolar VVI 100 bpm mode to exclude fusion beats. QRS duration was measured in 6fold magnification of the digital ECG (600%) 1) for the iQRS, 2) from the beginning to the end of the QRS in sHBP, 3) from the end of the pacing artifact to the end of the QRS in nsHBP, and 4) from the end of the pseudo-delta wave to the end of the QRS in nsHBP (see Fig.). Results In 388 patients (78±11 years, 38% female, 18% RBBB, 9% left bundle branch block) with an iQRS of 110±28 ms before implantation, sHBP was achieved in 206 patients (53%), nsHBP in 182 (47%). In sHBP, the pQRS was 88±18 ms, in nsHBP 123±18 ms including the pseudo-delta wave, 83±14 ms excluding the pseudo delta-wave. In sHBP, the pQRS was on average 15 ms shorter than the iQRS. In nsHBP, the pQRS was 9 ms longer than the iQRS when the pseudo-delta wave was included, and 31 ms shorter if it was excluded, the latter mostly due to correction of a RBBB by nsHBP. Conclusions In sHBP and nsHBP, very narrow pQRS durations of 80-90 ms can be achieved. The pQRS is frequently shorter than the iQRS, mostly by correction of a RBBB.QRS measurements in sHBP and nsHBP