In this paper investment and production costs for particleboard, dry and wet process hardboard and medium density fiberboard (MDF) are compared. The comparison is based on published data from the last three years, which are recalculated to an equal basis, i.e. for mills in Sweden ordered in the fall of 1975. For hardboard the dry process requires 10 to 20% lower investment than the wet process for mills with capacity larger than 150 tons/day. But the production costs are about 15% lower for the wet process than for the dry process, due to much lower costs for chemicals. The dry process MDF has 10 to 20% higher investment and production costs than particleboard. But for particleboard it is a large difference between published data in Scandinavia and in North America. The wet process MDF has higher investment per ton produced board than all other board types in this comparison. The return on investment is estimated for mills with a capacity of 300 tons/day. For hardboard the wet process seems to have a somewhat lower return on investment than the dry process when the comparison is made at the same product prices. But naturally the product prices, which are determined by the properties of the boards and by the market situation, are not the same for various types of board.