Modeling pressure drop, stationary-phase holdup and separation efficiency in centrifugal partition chromatography (CPC) are hampered by restricted knowledge concerning the flow behavior of the liquid-liquid two-phase system. A transparent column (type CPC-LLN) was constructed to determine the flow behavior as a function of the flow rate, rotational frequency and the properties of the two-phase system. Two main types of flow regimes, droplets and (broken) jets, are observed although the spraying regime hardly occurred Droplets occur at low flow rates and low rotational frequencies. The droplet regime changes into the (broken) jet regime when either the flow rate or the rotational frequency increases above a critical value. This critical value is described reliably by a dimensionless number correlation. A flow chart showing the type of flow regime as a function of the Weber number and the centrifugal force enables rational fine-tuning of operating conditions for given two-phase systems and equipment.