Aim: To evaluate prospectively the improvement in the signal:noise ratio (SNR), with the use of parallel technique in single breath-hold diffusion-weighted imaging (DWI) of the liver and its affect on apparent diffusion coefficient (ADC) measurements. Materials and methods: This study was approved by our institutional review board. Written informed consent was obtained from all participants. Fifteen patients underwent single breath-hold DWI of the liver with and without parallel imaging technique. SNR and ADC values were measured over a lesion-free right hepatic lobe by two radiologists in both series. When a focal hepatic lesion was present the contrast:noise ratio (CNR) and ADC were also measured. Paired Student's t-tests were used for statistical analysis. Results: Mean SNR values of the liver were 20.82 ± 7.54 and 15.83 ± 5.95 for DWI with and without parallel imaging, respectively. SNR values measured in DWI using parallel imaging were found to be significantly higher (p < 0.01). Mean ADC of the liver were 1.61 ± 0.45 × 10-3 mm2/s and 1.56 ± 0.28 × 10-3 mm2/s for DWI with and without parallel imaging, respectively. No significant difference was found between the two sequences for hepatic ADC measurement (p > 0.05). Overall lesion CNR was found to be higher in DWI with parallel imaging. Conclusion: Parallel imaging is useful in improving SNR of single breath-hold DWI of the liver without compromising ADC measurements. © 2006 The Royal College of Radiologists.