Recently, significant progress has been made in experimental studies on the flow of wet steam, measuring techniques based on recording the phenomenon of extinction of light and ultrasound have been elaborated or improved. The basic value experimentally determined in the final stage was the content of the liquid phase defined as the wetness fraction. The methodology of tests and experimental investigations was presented, as well as the applied and developed measurement systems. Next, some developed designs of new ultrasonic and light extinction measuring probe and their modifications are described. The article presents also some examples of applications of the developed measurement techniques in application to experimental research conducted on wet steam. Examples of comparison between experimental and numerical tests for the extinction method are also provided.