The results showed 52 percent were for legalization and 45 percent were against it. The survey was conducted between March 13 and 17 among 1,501 adults.
There has been a major shift in public opinion over the past few years, especially among young people. The poll showed that 65 percent of people between 18 and 32 years old favor legalizing the use of marijuana. That's up from just 36 percent in 2008.
Almost two-thirds believe the federal government should not enforce its laws against marijuana in states that allow its use.
A bill to allow Illinois residents to use medical marijuana in the treatment of their debilitating medical conditions was approved by the House Health and Human Services Committee last month.