Well, the answer is yes and no. Yes if the directory does not have over 4,000 listings and sell their toll free number to another treatment center! Regardless of the site activity, the sites page rank, your site will receive marginal results. However, if it is free...why not? If you are paying for this listing and the site offers a toll free number for intake calls, please pay special attention.
Two addiction treatment center directories of which I have talked to the developers, have no problem doing this. They just see it as "business as usual practice". In other words, the ends justify the means.
While these large sites sell their toll free phone number to your competitors, or the highest bidder, you are paying for a listing on this site? In my mind I find this to be a conflict of interest. The excellent directory web sites do not offer a toll free number for intake calls that over shadow your paid ads. The other thing I find interesting is that they do not disclose this information when you sign up and pay them, maybe if they did I would feel better about it, but not too much so. Essentially you are paying the directory site to send admissions phone calls to your competitors...hmmmm. Is that what you would like to do?
Once again, the old adage applies-BUYER BEWARE :) Best to have docs 2 disc consult with you on what directories to consider. Any more, with social networking changing how we do internet marketing, listing on a directory is a tired application, and only a very small piece of the whole puzzle.