Characteristics of in flight particles before they impact on the substrate influence strongly the quality of coating obtained by plasma spraying. Various optical techniques can be used to measure the in-flight particle characteristics; some of these techniques require the use of high- speed two-color pyrometers to collect the light emitted by the particle during the in-flight period when they pass through the measurement volume. However, the intense radiation coming from the plasma can affect the particle thermal radiation and lead to erroneous measurements. This work was dedicated to the study of reflected light coming from the plasma and scattered by the injected particles. To achieve this goal, sprayed particles were analyzed by optical emission spectrometry. The light scattered by the particles was found to influence significantly the measured temperature. This work allows thus the estimation of the accuracy of temperature measurements on particle surface for the thermal spraying process. Abstract only; no full-text paper available.