Local measurements and 3-D CFD simulations in Gas-Liquid cylindrical Cyclone (GLCC©) separators are scarce. The main objective of this study is to conduct local measurements and 3-D CFD simulations to understand the swirling flow behavior in a cylindrical cyclone with one inclined tangential inlet. Axial and tangential velocities and turbulent intensities across the GLCC© diameter were measured at 24 different axial locations (12.5″ to 35.4″ below the inlet) by using a Laser Doppler Velocimeter (LDV). The liquid flow rate was 72GPM, which corresponds to an average axial velocity of 0.732 m/s and Reynolds number of 66,900. Measurements are used to create color contour plots of axial and tangential velocity and turbulent kinetic energy. Color contour maps revealed details of the flow behavior. Additionally, 3-D CFD simulations with different turbulence models are conducted. Simulations results are compared to LDV measurements.