The functional format resume has few benefits and many detriments. Someone who chooses the functional format resume generally does so when a career change is in the works or there is something in his background that could be a problem. Often, the functional format resume is used when a prison term or some other large span of time is lost out of work history. Job seekers who want to change fields will sometimes opt for the functional format in an attempt to highlight the skills they have that make them qualified for the new field.
A functional format resume has the content arranged according to performance type (thus, function). The resume is divided into categories of skill and function. Under each skill category, the relevant information would be listed or described. A brief work history listing would come at the end of the document that lists job title, employer, and dates. Some purely functional resumes don't have the work history section at all and no dates appear on the resume.
There are many reasons NOT to use the functional format resume. Recruiters really hate the functional format because it makes them hunt for the information they seek and recruiters simply do not have time to hunt for information or make assumptions. Employers don't hire potential - they hire past performance. Future performance of a new hire is predicated on past performance. Recruiters and hiring managers want to see past performance in a resume so they can make a judgment on the future performance potential of a candidate. A functional format resume doesn't allow them to make that assessment.
The functional format takes away all frames of reference for hiring managers to measure what skills and abilities are listed. A candidate might claim high sales abilities and track record in the functional resume, but the recruiter is unable to place that in context in terms of time, employer, situation, or history.
Functional resumes tend to be quite short, too. The brevity of the resume doesn't help it in online databases because keywords are fewer. By eliminating job descriptions and other information that naturally comes into a chronological format resume, keyword richness is decreased resulting in poor performance in online databases.
Finally, recruiters and hiring managers realize the functional format is used to attempt to cover up detrimental factors in a candidate's past. They aren't stupid! Instead of helping to disguise problems in a career history, the functional format actually highlights them! Even if no problems exist in the background of a candidate who uses a functional format, the reader will assume there is something there.
Despite all the problems with functional format resumes, job seekers still feel compelled to use them, even when a chronological format would serve better. It's bothersome to hear a job seeker report he has sent out over a hundred resumes with no response and discover he's been using a functional format all along. What a waste of time and first impressions!