YOUNG people arrested by police in Calderdale will be tested for drugs.
Drug testing of child suspects as young as 14 will begin within days, Government ministers announced.
Home Office minister Caroline Flint launched a new programme in 10 pilot areas across England, including Calderdale and Bradford.
Adults suspected of a series of property crimes, such as burglary, car crime and theft, have been tested for cocaine, heroin and crack when charged by police in Calderdale and Bradford since April last year.
From Saturday, children aged 14 to 17 will be tested for the same three Class A drugs when charged with similar crimes.
Those who test positive for any of the three drugs are offered voluntary treatment.
A Home Office spokeswoman said: "Evaluation results show that drug testing, while it does not reduce the number of people taking Class A drugs, does highlight those who are and enables them to get treatment."
A West Yorkshire Police spokesman said offences which would see suspects tested included theft, robbery, burglary, obtaining property by deception, and handling stolen goods.
A young person charged with any other offence could also be tested if an inspector suspected drugs had caused or contributed towards the offence.
The test is painless and involves a mouth swab. Results for cocaine and heroin can be read within minutes.
Anyone arrested is given the opportunity to see an enhanced arrest referral worker - formerly known as a drugs worker - who can help them into treatment. They are also encouraged to see an arrest referral worker if they test positive for Class A drugs.
An appropriate adult must be present in the police custody area when young people are tested.
Asst Chief Constable Greg Wilkinson said:
"This is part of our wider strategy to prevent and deter young people from wasting their lives with drugs and crime."
National government figures show that in adult tests in May, nearly half proved positive.