The purpose of this work is to find a correlation for heat transfer to walls in circulating fluidized bed (CFB) boilers. Heat transfer and suspension density data from six boilers in the range from 12 to 300 MWth, form the basis of the correlation. The data were averaged over the entire height of the heat-receiving wall to facilitate application to boilers. Averaging also reduces uncertainties in the measured data. The correlation of heat transfer coefficient (HTC) and average suspension density represents the measured heat transfer coefficients within 15%. An attempt to separate radiation and convection was made in order to account for variations in wall and bed temperatures. The improvement due to the separate treatment is not significant compared to the uncertainty in the experimental data, but the influence of temperature on the heat transfer coefficient is explicitly represented.