This paper details the non-intrusive optical measurement of droplet size distribution in two-phase flashing propane jets, by the use of a diffraction-based technique. Centreline and lateral profiles of droplet size are presented. The data are compared with previously published data from similar flashing jets. The importance of careful and detailed data analysis is highlighted, to ensure that only valid data are obtained and reported, especially in the near-field regions of such jets. Even with considerable data analysis and evaluation, this technique may only be able to provide lower accuracy quantitative information and qualitative droplet size distribution trends. Crown