In the individual insurance plan market, just 400,000 people, or 2.2 percent of the overall market, had plans canceled after they received a letter citing lack of Obamacare compliance for the action. Another 3.4 percent, or nearly 600,000 people, were canceled for unknown reasons, the report found.
The individual market before Obamacare was extremely volatile, with less than 50 percent of customers staying in their plan for a year or more, the report noted.
The report said that another 500,000 people who had insurance through their job, so-called group coverage, had their health plans canceled for 2015 explicitly due to lack of compliance. That represents just 0.3 percent of the total employer-based insurance market.
Read MoreHuh?! Forced by your job to buy health insurance?
An equivalent number of people in the employer-based market had plans canceled for an unknown reason, according to the study.
The report doesn't estimate how many people who had existing plans canceled for this year went on to obtain health coverage through other individual and job-based insurance.
The study's lead author, Urban Institute's senior health economist Lisa Clemans-Cope, said certain numbers of people would have likely bought federally subsidized coverage through government-run Obamacare exchanges or gone on Medicaid.
Even with the cancellations, the rate of people without health insurance in the United State continues to hit record lows.
In another report Thursday, the Urban Institute found that the rate of non-elderly adults without insurance as of last December was just 12.8 percent, compared with 17.7 percent in September 2013, on the eve of the launch of Obamacare insurance marketplaces. The drop in the uninsured rate is due largely to an increase in the number of people covered by the government-run Medicaid program and by sales of individual policies on the Obamacare exchanges.
Read MoreRetirees may shell out $220K for health care
Clemans-Cope said that the plan cancellations, which made headlines in the late fall of 2013, "wasn't such a big story in the fall [of 2014] because the numbers are so low."
"There are lot of processes in place to help consumers transition," she said. "The [Obamacare] marketplaces are running more smoothly than last year, and insurers are required to inform consumers about their options." In 2013, insurers had not been required to tell customers whose plans were being canceled that they might be able to buy subsidized coverage through the government marketplaces.