As Paul said, you really need to understand parameter sniffing to resolve this correctly. The performance impact *may* be due to recompiling every single time this proc is executed - if that is the case then try just recompiling the statement. If that does not work then a solution would be to change the proc to call one of two children - one for the "all" cases and the other for the filtered cases. You may not need any recompile statements then.