For college students, it's that time again—hunting for a summer internship.
Internships have become increasingly important as job candidates attempt to stand out in a challenging job market. But the type of internship you land can make all the difference.
Paid internships markedly increase a student's chances of landing a job by graduation. But unpaid gigs provide little or no edge over not interning at all, according to a survey by the National Association of Colleges and Employers.
(Read more: Rallying cry against unpaid internships grows)
In the association's most recent annual survey of students, conducted last spring, 63 percent with paid internships had landed jobs before graduation. Even accounting for gender and industry, just 37 percent of students with unpaid internships were that successful, barely more than the 35 percent of students with no internships who had landed jobs.
"The unpaid internship had no impact relative to having no internship, at least in terms of getting a job," said Edwin Koc, director of strategic and foundation research.
(Read more: Unpaid interns pose new challenge for job seekers)
The salary difference between paid and unpaid internships was also large: Those with paid internships who landed jobs got starting salaries averaging $51,900, well above the $35,700 offered to students with unpaid internships. (Students with no internships actually had a slightly higher starting salary—$37,100—but Koc said the difference is not statistically significant.)
Pay for internships can vary widely, from thousands of dollars a week at a tech company to a nominal amount at a small organization.
(Read more: Wall Street slips out of highest paid intern list)
Even so, many paid internships are at least as hard to land as the unpaid kind. So what's a student to do?
Career development offices on campus and academic advisors are a great place to start. They often have plenty of internship listings, and some of them may not be advertised widely.
Various websites also feature listings of available internships. For example, idealist.org lets users search for paid internships with nonprofits, filtering by industry and location. Simplyhired.com offers similar search capabilities for internships with for-profit employers, as does internmatch.com.
Then there are start-ups like Flinja, which operates online marketplaces for freelance work and internship via websites open to students at different colleges and universities. At the University of Southern California, for example, students signed up with Flinja can post services they want to provide, and staff members and alumni can log on and book jobs. Internships may or may not be available, but students do gain paid work experience and build their networks.
Sam Larkan, a recent New York University graduate, found her paid internship at The Child Center of NY the old fashioned way, on campus. "My advisor emailed me the posting to The Child Center, so I applied," she said. She had had two internships in the past at Conde Nast, but they were unpaid except for a stipend at the end, she said.
Larkan found her work at The Child Center, a nonprofit that helps at-risk children and youth, more challenging than her earlier experience. She worked on grant proposals and communications and helped launch a new event for young professionals.
"I felt more like an employee than an intern at The Child Center," she said. "At Conde Nast I got to do a little more the second time I worked there, but in a large corporation it was just going to be lesser work."
After graduating from NYU, Larkan landed a job as the program assistant with the Center for Women and Enterprise in Boston. She believes her Child Center experience was instrumental in helping her land the job.
The Conde Nast experience "always stood out because it's such a well known name, but I think the level of work that I was able to put on my resume for The Child Center really stood out," she said.
Laura Schenone, director of grants and internships at The Child Center, said the decision to pay an intern was strategic. "When we set out to hire an intern, we made a decision early on that if it was an unpaid internship we wouldn't be able to expect high performance," she said.
"We are a lean nonprofit, and so overhead is very tight. But in the long run it was a good investment for us. By paying an hourly rate, we raised expectations and we were the winners in the deal. She delivered more than she got."
—By CNBC's Kelley Holland. Follow her on Twitter