Perforated piles are used in near-shore breakwaters for coastal protection and deep water platforms for oil exploration. Emerged and submerged perforated cylindrical structures reduce wave-structure interactions and scouring problems considerably, but their use on a floating structure is limited. Mathematical model is developed to introduce perforated walls in floating structures and method of solution is discussed. Eigenfunction expansion approach is used to derive velocity potentials based on which hydrodynamic forces on perforated cylinders are obtained. An example tension leg platform having perforated caissons is chosen; length of the perforated region and its location on tension leg platform are varied to determine their influence on its motion. For increase in perforation length, fluid-structure interaction reduces, causing decrease in surge and pitch responses. However, increase in perforated length in the lower part of column does not significantly increase these responses; heave remains relatively unaffected regardless of the length of perforation in the columns. © 2010 Taylor & Francis.