Purpose:The purposes of this work are to develop 4D‐CBCT imaging system with orthogonal dual source kV X‐ray tubes, and to determine the imaging doses from 4D‐CBCT scans.Methods:Dual source kV X‐ray tubes were used for the 4D‐CBCT imaging. The maximum CBCT field of view was 200 mm in diameter and 150 mm in length, and the imaging parameters were 110 kV, 160 mA and 5 ms. The rotational angle was 105°, the rotational speed of the gantry was 1.5°/s, the gantry rotation time was 70 s, and the image acquisition interval was 0.3°. The observed amplitude of infrared marker motion during respiration was used to sort each image into eight respiratory phase bins. The EGSnrc/BEAMnrc and EGSnrc/DOSXYZnrc packages were used to simulate kV X‐ray dose distributions of 4D‐CBCT imaging. The kV X‐ray dose distributions were calculated for 9 lung cancer patients based on the planning CT images with dose calculation grid size of 2.5 × 2.5 × 2.5 mm. The dose covering a 2‐cc volume of skin (D2cc), defined as the inner 5 mm of the skin surface with the exception of bone structure, was assessed.Results:A moving object was well identified on 4D‐CBCT images in a phantom study. Given a gantry rotational angle of 105° and the configuration of kV X‐ray imaging subsystems, both kV X‐ray fields overlapped at a part of skin surface. The D2cc for the 4D‐CBCT scans was in the range 73.8–105.4 mGy. Linear correlation coefficient between the 1000 minus averaged SSD during CBCT scanning and D2cc was −0.65 (with a slope of −0.17) for the 4D‐CBCT scans.Conclusion:We have developed 4D‐CBCT imaging system with dual source kV X‐ray tubes. The total imaging dose with 4D‐CBCT scans was up to 105.4 mGy.