European efforts to curb cocaine and heroin use made little impact in the past year, the EU's main drugs watchdog says in its annual report.
But cannabis use, particularly among young people, is declining, according to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA).
Heroin use in Europe is "stable but no longer diminishing", the EMCDDA says.
Combinations of drugs pose increasing problems, as do new synthetic drugs, many of them marketed on the internet.
"There is little to suggest any improvement regarding cocaine and heroin use in Europe, the two substances that remain at the heart of Europe's drugs problem," the EMCDDA says.
It estimates there are up to 1.5 million regular opiate users in the EU and Norway, most of them heroin users.
In 2007, 13 of the 18 reporting countries showed a rise in drug-induced deaths compared with 2006, most of them attributed to heroin. Before 2004 the numbers of drug-induced deaths had been declining.
New cocaine routes
The EMCDDA says most of the countries surveyed reported a stable or rising trend in cocaine use in the 15-to-34 age group.
Cocaine use among young adults ranged from 3.1% to 5.5% in the countries most affected - Denmark, Ireland, Italy, Spain and the UK.
graph of top five countries where young adults use cocaine
The report says there have been "considerable" falls in the purity of cocaine marketed in the UK.
"These data could suggest declining cocaine availability, but other information puts this conclusion into question.
"The number of seizures of the drug is still increasing, prices are falling, and there are suggestions of a switch to new trafficking routes through Eastern Europe, which may have impeded interdiction efforts," the EMCDDA says.
What is new is the wide range of substances now being explored
Cannabis use however is declining, particularly among children aged 15 and 16, the report says.
This contrasts with the 1990s, which saw a dramatic rise in cannabis use in Europe.
The report says national and EU policy "may have played a part" in triggering the decline, "but declining levels of use are also seen in the USA and Australia, suggesting that broader sociocultural factors are likely to be important".
The EU's drugs early-warning system, set up in 1997, is helping to detect new "designer" drugs, the EMCDDA says, but sellers are using sophisticated methods to circumvent the law.
In 2008, 13 new synthetic drugs were reported to the EMCDDA, six of them derivatives of cathinone, a substance found in the mildly narcotic khat plant.
The synthetic cannabis substitute Spice was offered by 48% of the 115 online drug retailers surveyed in 2009. Of those retailers, 42% were UK-based.
According to EMCDDA director Wolfgang Goetz, "what is new is the wide range of substances now being explored, the aggressive marketing of products that have been intentionally mislabelled, the growing use of the internet, and the speed at which the market reacts to control measures".
The stimulant methamphetamine, which has been concentrated in the Czech Republic, is now becoming more available in northern Europe, including Norway and Sweden, the report says.