As you say the overhead should be similar to Nullable. And the struct should be allocated on the stack, but the CLR doesn't guarantee that, so it can be on the

As you say the overhead should be similar to Nullable. And the struct should be allocated on the stack, but the CLR doesn't guarantee that, so it can be on the heap too. There is however an 'if' in the constructor of Option<T>, so there's a little extra potential branching overhead. For most scenarios I suspect this is all moot, but if you're looking for the absolute maximum performance then you would probably want to do some profiling before committing too heavily.