An Institutional Review Board (IRB) had been approved to retrospectively analyze DIBH patient data. The stored motion log files (that contain the translational and rotational displacement data over time) for 30 patients treated with tangential fields for left‐sided breast, delivered during DIBH, in our clinic from 2012 and 2013 were analyzed. Fractionation schedules included 200 cGy×23 fractions (11 patients), 267 cGy×16 fractions (10 patients), 200 cGy×25 fractions (8 patients), and 180 cGy×28 fractions (1 patient). The internal mammary nodes (IMN) were intended to be included in the tangential fields in 10 patients. Whenever IMN was included as part of the tangential beams, the volume of the IMN covered by 40 Gy was evaluated. If part of the IMN was not covered by 40 Gy, a separate electron boost might be needed to bring IMN to the desired dose. Electron boost is beyond the scope of this study, and will not be discussed here. Since the IMN is always at the edge of the tangential beams, even a small amount of motion might affect its coverage. Therefore, we included the IMN coverage in this study, as well.