Now this depends upon what experience you mention you have in first place. If the times you have worked don't add up then the recruiter will express a doubt. These doubts could be on various topics like experience gaps, academic gaps, and so on. Perhaps you may have done consultancy work, volunteering or something similarly useful but if you don't show that in your resume, it lets enough room for doubt. So, first thing that you should do is show all your experience, relevant or otherwise, on your CV.
Next, about the gaps, I must tell my personal experience. I worked at a place for three months on contract and then was asked to resign because I had failed in my final year exams. In the next six months I cleared those papers and got another job. Later when I went looking for a better job, a lot of recruiters asked me the reason behind the gap. Most of the times I'd tell them the half-truth - that it was a contract job. The next question was inevitable- "How can we trust you if you can hop a job in months?" That would always leave me speechless. Finally once I told a recruiter the whole truth- that I failed and got fired. They did not grill me further, instead hired me for the profile I wanted and a pay beyond my expectations. Sometimes it is best we tell the whole truth.