The New York medical marijuana law is far more restrictive than the laws in Colorado and many other states, and one that doesn’t go far enough for advocates and patients.

Gov. Andrew M. Cuomo, a onetime opponent, reversed his position in January when he announced a plan to allow 20 hospitals across the state – including Roswell Park Cancer Institute – to serve as dispensaries for medical marijuana.

The State Legislature passed its own, more-expansive version, and reached a deal with the governor in June following intense negotiations.

Roswell Park will not have a formal role under the law, with Dr. Donald L. Trump, the president and CEO, calling that a lost opportunity for cancer center scientists to take part in needed studies of medical marijuana.

New York’s law has strict limits on which illnesses can be treated with marijuana. The approved conditions include cancer, Lou Gehrig’s disease and multiple sclerosis, but patients who have other conditions argue the list is far too restrictive.

“This is a starting point. As we move forward, we will evaluate the data and research to determine what new diseases may be added, and we will modify the program accordingly,” said Dr. Howard A. Zucker, the acting health commissioner.

Under the law, patients can inhale the marijuana as a vapor, or consume the drug in an edible format, but they aren’t allowed to smoke it.

Further, not every doctor will be allowed to prescribe marijuana. Those who wish to do so must register with the Health Department, and the state plans to keep close track of both the prescribers and the recipients, as it already is doing with prescription drugs.

The law directs the Health Department to select five organizations, or companies, that will produce and distribute medical marijuana in New York.

They will operate four marijuana dispensing sites, for a total of 20 across the state, though the state’s health commissioner can add more if needed. Critics say a state as large in size and population as New York needs far more than 20.

“Where I live, within a few blocks, there are 20 CVS drugstores,” said Assemblyman Richard N. Gottfried, D-Manhattan, who had unsuccessfully sponsored medical-marijuana legislation since 1997.

Patients won’t be able to get a prescription for 18 months, and advocates say that is far too long for people in pain to wait.

State health officials said the restrictions are necessary to avoid abuses of the law. “We’re treating this like medicine in every way, shape or form, including how it’s produced and how it’s dispensed and how it’s used,” said Terence J. O’Leary, director of the department’s Bureau of Narcotics Enforcement.

Gottfried said he believes the law is the best that supporters could get this year, but the need to amend the law is “extraordinarily urgent” for many patients, including children with Dravet syndrome, a rare and devastating form of childhood epilepsy. Cuomo said in late July that he wants to get medical marijuana to children with epilepsy in less than 18 months.

“It’s a good law that’s going to relieve suffering and lengthen life for thousands and thousands of people,” Gottfried said. “Some provisions that were added will seriously limit its effectiveness, and I hope we can make some changes in the next session.”