The axial solid distributions in a circulating fluidized bed of 10 cm i.d. and 4 m height have been studied. These distributions are measured at room temperature with two solids (sand and coal) from group B of the Geldart classification, as a function of air velocity and solids flux. These profiles are S-shaped or non-S-shaped depending on the operating conditions, and are similar to those reported in the literature with other types and sizes of solids. The Kunii and Levenspiel exponential-decay model for the axial voidage profiles has been modified to consider a freeboard height lower than the transport disengaging height (TDH), developing some equations to obtain the axial voidage profiles at heights lower than the TDH. Two equations have been proposed to calculate the K constant and the decay constant a as a function of the operating conditions. The modified model gives a good fitting of the experimental results obtained in this work and those obtained by other authors in different conditions and experimental set-ups.