Abstract Viscosity measurements were performed with a falling cylinder viscometer on difluoromethane (R32) and the refrigerant blend R410A (R32 + R125 with 50% by mass) at the temperatures 313.15 K, 348.15 K, and 393.15 K with pressures of 350 MPa. The measurement results are compared with literature data and with data calculated using an extended corresponding states (ECS) model. The agreement with literature data is closer for R410A than for R32 while the deviations from the ECS model are higher for R410A than for R32. Correlations that represent the new results as functions of temperature and pressure within their uncertainty are also reported.