This is according to Rebecca Lieb of Econsultancy, who told bMighty that SEO can be viewed as the online equivalent of putting up a sign outside a physical store.
Business could be lost to competitors if SMEs do not ensure their organisations show up in the relevant search results pages, she warned.
Those starting out with SEO should carry out the right keyword research to make sure they pick terms that are the most appropriate for the consumers they are targeting, Ms Lieb said.
She advised: "The more specific the term, the closer the searcher is to making a decision or a purchase.
"People are in research mode or in buying mode and you want to optimise your site for terms those searchers use."
Almost 90 per cent of small firms think they may be missing on opportunities to expand their operations online, according to a poll carried out by Microsoft adCenter last year.