The number one misconception people have is that a designer and a decorator are the same when there is a clear and distinct difference between the two. Many people think they need an Interior Designer when a Decorator will suffice.
Decorators are not required to attend an accredited program or undergo a state licensing whereas Interior Designers are duty-bound to respect public welfare and design spaces that are universally accessible. It is a no-brainer when designing a commercial space as to which professional to move forward with, Interior Designers understand code requirements under commercial construction. As for residential design, you have more leeway in your decision.
Although an Interior Designer is going to have a better understanding of adjacencies and space planning techniques that can really transform your interior, a Decorator can accommodate surface aesthetics and accessories.