The cedar planks that you can buy at the grocery store for cooking salmon on are simply western red cedar boards. Save yourself some cash and buy a cedar fence picket. Make absolutely sure that the wood is not treated with anything before use. You could also use any locally grown cedar that you can get into planks. As far as using that cedar for smoking I can only imagine that it would taste very strong. I would not reccomend that.

When cooking with a plank of cedar the fish is not exposed to that much smoke. Smoking the fish takes a long time - several hours. Cooking is done in a few minutes with a plank soaked in water. Much less opportunity for the smoke to strongly flavor the fish.

Steve