Abstract The article describes three interlaboratory experiments concerning ²²²Rn determination in water samples. The first two experiments were carried out with the use of artificial radon waters prepared by the Laboratory of Radiometric Expertise (LER), Institute of Nuclear Physics, Polish Academy of Sciences in Kraków in 2014 and 2018. The third experiment was performed using natural environment waters collected in the vicinity of the former uranium mine in Kowary in 2016. Most of the institutions performing radon in water measurements in Poland were gathered in the Polish Radon Centre Network, and they participated in the experiments. The goal of these exercises was to evaluate different measurement techniques used routinely in Polish laboratories and the laboratories’ proficiency of radon in water measurements. In the experiment performed in 2018, the reference values of ²²²Rn concentration in water were calculated based on the method developed at LER. The participants’ results appeared to be worse for low radon concentration than for high radon concentrations. The conclusions drawn on that base indicated the weaknesses of the used methods and probably the sampling. The interlaboratory experiments, in term, can help to improve the participants’ skills and reliability of their results.