Hi Gus! The best pace to start would be the Department of Consumer Affairs for your region. They have alot of answers on their website at Oregon.gov
Report Kay's answer
Gus, If you are the sole owner and sole worker then no you do not. If you did you would just be paying yourself. However, if you have anybody (even just 1 person) working for you that is NOT an owner of your company then you need to have workman's comp.
Report Chuck's answer
Gus, the laws vary from state to state regarding Worker's Compensation Insurance. Consult your state Department of Labor for the answer that applies to your specific situation.