This study was undertaken to investigate and compare the accuracy and reliability of dual image and extended field-of-view (EFOV) ultrasound (US) techniques in distance measurements using acoustic phantoms. Ten tissue phantoms were constructed and were scanned twice with an interval of 3 days by two operators. Measurements of various known distance (ranging from 4.6 to 7.2 cm) in the phantoms were made with dual image and EFOV US. Results showed that both dual image and EFOV US have a high accuracy and reliability in distance measurements, with the EFOV US (r = 0.997 to 0.998, reproducibility = 99.8%, repeatability = 98.2 to 99.8%) being slightly more accurate and reliable than dual image US (r = 0.948 to 0.981, reproducibility = 94.6%, repeatability = 89.6 to 97.9%). EFOV US has a higher accuracy and reliability than dual image US in distance measurements. However, the dual image US is a useful alternative with a high accuracy and reliability when EFOV US is not available. ; School of Optometry