Purpose: “Flash Spiral” imaging is a new prospective ECG-triggered spiral scan mode that uses a very high-pitch for coronary computed tomography angiography (CTA). This enables complete image acquisition within one cardiac cycle with a very low radiation exposure. The aim of this study was to investigate the diagnostic accuracy, image quality, and effective radiation dose of prospectively ECG-triggered high-pitch spiral method (Flash spiral mode) of coronary CTA using dual-source technology for the evaluation of coronary artery stenoses. Material and methods: The study included 186 consecutive patients (115 men, 71 women; mean age: 53.37 years) who underwent coronary CTA. Coronary CTA was performed with a 128 × 2-slice dual-source CT (Somatom Definition Flash, Siemens, Germany) using a prospectively ECG-triggered high-pitch spiral mode. Patients were divided into three groups according to heart rate (≤ 65 bpm, 66–75 bpm, ≥ 76 bpm) and body mass index (BMI) (20–24 kg/m2, 25–29 kg/m2, 30–34 kg/m2) values. The correlation between heart rates, image quality and BMI values are investigated. A four-point scale (1 = excellent, 4 = poor/non-diagnostic) was used to rank the comparative image quality. Effective radiation doses were calculated. Also the correlation between radiation dose, sex and BMI values were investigated. In addition, diagnostic accuracy of CTA for detection of significant (≥ 50%) coronary artery stenoses was compared with invasive coronary angiography findings of 612 vessel segments in 38 patients. The sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy rate were calculated. Results: A total of 2976 coronary artery segments were present. Of all coronary artery segments, 2381 (80%) had an image quality score of 1, and 1.5% segments were rated as “poor/non-diagnostic”. When the correlation between heart rate and image quality is investigated, there was a significant difference between ≤ 65 bpm and ≥ 76 bpm groups. However, there was no significant difference between ≤ 65 bpm and 66–75 bpm groups. The mean effective dose was found as 1.3 mSv (min: 0.5, max: 2.4 mSv). The correlation between effective radiation dose and BMI was moderate. However, the correlation between gender and radiation dose was significant. Sensitivity, specificity, negative predictive value and accuracy of coronary CTA on a per-vessel segment were 90.1%, 97.4%, 98.6%, and 96.5%, respectively. Conclusions: Prospectively ECG-triggered high-pitch spiral mode coronary CTA provides high image quality and diagnostic accuracy, with very low radiation dose for evaluation and exclusion of coronary artery stenoses.