Experimental, data on the pressure-density-temperature relation are reported for tiro fluorinated alkenes that meet the criteria of the potential new-generation refrigerants with considerably low global warming potential (GWP) and the zero ozone depletion potential (ODP). The data for 2,3,3,3-tetrafluoroprop-1-ene (R-1234yf) and 1,1,2,3,3,3-hexafiuoroprop-1-ene (R-1216) were obtained with a constant volume apparatus at temperatures from (217 to 353) K and from (208 to 353) K, respectively, and at pressures from (1 to 40) MPa. Thus, the temperature-pressure region covered with experimental p-rho-T data has been substantially extended for both substances. The combined uncertainty at the 0.95 confidence level of the reported density data takes its maximum value at the lower end of the temperature interval: 1.2 kg.m(-3) (9.10(-4) rho) for R-1234yf and 1.4 kg.m(-3) (10(-3) rho) for R-1216. The root-mean-square deviation of the reported data from the Helmholtz free energy equation of state fitted to them is 0.18 kg.m(-3) (1.6.10(-4) rho) for R-1234yf and 0.28 kg.m(-3) (2.1.10(-4) rho) for R-1216.