Damping plates are generally used to reduce the response of floating platform by increasing the added mass and damping. Heave and pitch responses of spar platform with single and double damping plates under regular waves are discussed in this paper. Regular wave experiments are conducted on 1:50 scale spar hull with damping plate. Heave and pitch response amplitude operators (RAOs) are obtained numerically using Boundary Element Method (BEM) based software ANSYS-AQWA and compared with the model test results. Parameters of scaling ratio, damping plate diameter to spar diameter ratio, damping plate position to spar draft ratio and spacing between the double damping plates to spar draft ratio are considered for the numerical analysis. It is found that the heave and pitch RAOs reduce with an increase in scaling ratio. Diameter ratios of 1.2–1.4, position to spar draft ratio of 0.16 and spacing to spar draft ratio of 0.16 are suggested for reducing the heave response. Similarly, diameter ratios of 1.2–1.4, position to spar draft ratio of 0.12 and spacing to spar draft ratio of 0.2 are recommended for pitch response reduction. © 2021 Elsevier Ltd