However, this is a case where you’ll want to use your common sense. If you went to college for marketing and had a marketing internship your senior year, then worked as a server for the next several years, you would want to include your marketing internship.
One of the biggest mistakes you can make when applying to jobs is sending the same generic resume out for each one. Sure, you can apply to more jobs if you don’t take the time to personalize your resume each time, but chances are you won’t get interviews from any of them. If you take the time to tailor your resume, even though you’ll be applying for fewer jobs, you’ll get more interviews.