Experimental studies of liquid-liquid Taylor-Couette-Poiseuille flow were conducted using various fluids, and the effects of the physical properties (density, viscosity, and interfacial surface tension) and the operational parameters (feed composition and inner cylinder rotation rate) on the vortex structure were investigated. Depending on the operating conditions, one of three distinct flow patterns was observed: (1) a translating banded structure, (2) a spatially homogeneous structure, or (3) a pattern of alternating regions composed of the structures 1 and 2. Two empirical equations were developed to describe boundaries between these different flow patterns. The phase boundary between structures 2 and 3 is a function of the Weber number, whereas the boundary between regions 1 and 2 is a function of the Reynolds number.