In this work a novel measurement technique for pseudo-2D fluidised beds is developed. The objective is to give an estimation of the overall frictional force between the solids and the front and rear walls of the bed. For doing this, the measured pressure signal in the bed is processed in combination with the solids distribution (i.e. centre of mass position, velocity and acceleration) obtained from digital image analysis of the optically accessible front view of the bed. This is performed by acquiring the pressure signal in the bed simultaneously to the digital images. Both the pressure and the digital images are connected through a simple force balance in the bed, and a particle-wall interaction coefficient is obtained assuming that the overall frictional force is proportional to the centre of mass velocity. The particle-wall interaction coefficient found using this technique is of the order of 40-120 kg/m(2) s in the bed tested, and the standard deviation of the frictional forces reaches more than 70% of the weight of the bed. Therefore, the results indicate that the contribution of the particle-to-wall friction on the fluctuation of the pressure drop in a pseudo-2D bed is not negligible. (C) 2013 Elsevier Ltd. All rights reserved.