A total of 169,000 Spaniards began using cannabis in 2013 compared to 142,000 who started to smoke tobacco, according to the latest annual health ministry study of drug use in Spain.
More than one-third of new users, 61,000 or 36 percent, were between the ages of 15 and 17, the study showed.
The number of cannabis users overall was slightly down but the number of people who use the drug on a daily basis has increased.
"The figures confirm the extension of the problematic pattern of consumption of this substance," the head of the government's National Drugs Plan, Francisco Babin, said in a statement.
Of Spaniards aged 15 and 64, 9.2 percent said they had smoked cannabis within the last year, down from 9.6 percent in the previous study carried out in 2012.
But the percentage who said they smoked marijuana on a daily basis rose to 1.9 percent in 2013 from 1.7 percent in 2012.
Over 700,000 Spaniards between the ages of 15 and 64 meet the criteria for a diagnosis of a "problem user" of this drug, the study found.
Spain's proximity to Morocco, one of the world's principal producers of cannabis, has made it the main gateway into Europe for the drug.
Since June 2013, Spanish authorities have seized more than 100 tonnes of hashish in various operations.