I am beginning to think that one of the most misunderstood roles in corporate America is that of the chief operating officer.

Like others, I have viewed the COO of a hospital or health system -- or any other kind of company for that matter -- as a sort of CEO-in-waiting, performing some of the functions of the chief executive under the big dog's mentoring eye. Thus, when it came time for the COO to move up to the CEO's chair, he or she would be ready for a seamless transition.

Frankly, most of my assumptions about the COO position were just plain wrong.

I had a revelation about this only recently, and when I realized how wrong I have been over the years I was embarrassed. Actually, an informal survey I did of business associates confirmed that I am not alone in misperceiving the import of the COO. The job turns out to be much more complicated and sophisticated than I would would have ever suspected. Now that I have gained enlightenment, I'm glad to share my insights with readers.

My revelation stems from a conversation I had with a friend of mine one recent morning over breakfast. He was involved in a search for a COO in his role as a member of a company's advisory board. The company had just hired an executive recruiting firm for the post. In preparation for the search my friend had spent a lot of time learning about COOs and their roles by reading various articles and a 2006 book entitled Riding Shotgun: The Role of the COO, by Nathan Bennett and Stephen A. Miles. Today it is considered the definitive work on this position, providing insights into what the authors say is a little understood role.

I immediately got a copy of this interesting book.

The authors have developed a framework for understanding who the COO is, why a company would want to create this position and the challenges associated with successful performance in the COO role. One reason to hire a good COO is when a company has reached a certain level of success, but the CEO can't maintain operations alone. There needs to be an executive whose focus is execution, making sure goals are met both externally and internally. This is the person, the authors write, who makes sure "the trains run on time." While the CEO figures out strategy for where the company is headed, the COO is the person who gets it there, doing the nitty-gritty detail work and making sure the CEO is informed on all necessary matters.

It is critically important that the CEO and COO have good chemistry and complete trust in each other. As a matter of fact, in Riding Shotgun: The Role of the COO, a director of Starbucks opines that, "Deep down, (the CEO and COO) have to trust each other and you have to like each other. If you don't trust each other ... it may work, kind of, but it will be at a 50% level at best."

Yes, the COO can be the heir apparent as well. In fact, today there is great emphasis on CEO succession planning, which makes having a top-drawer COO even more important. And when the CEO is an underperformer, a good COO is golden.

Paula Rosput Reynolds, who has served as CEO of a number of different large companies, including Safeco and Preferwest, warns: "Under a weak CEO, the job (COO) is nothing short of agony. Under a great CEO, the COO's job is the best in the world, grounded in execution and performance metrics."

I believe working for a weak CEO under any circumstances is not necessarily a bed of roses for anyone in a given organization. But a strong CEO, complimented by a strong COO and backed up by other competent executives, is a winning combination for any business.

Thanks to my breakfast companion, I found out about Riding Shotgun: The Role of the COO, and now know much more about the true value of a great COO. I won't repeat my mistake of assuming that the second banana in an organization is any less important than the first.