Computer-based therapy should be available to all patients in England from April, says the government.
Computerised CBT has been shown to help patients with depression
Patients with mild depression or anxiety should receive therapy instead of drugs, but there are long waiting lists around the country.
A trial of one computer programme - 'Beating the Blues' - found it more cost-effective than other treatments.
But experts warned computer-based therapy was not for everyone and access to therapists also needs to improve.
The Department of Health has issued new guidance for primary care trusts on how to implement computer-based therapy.
It is estimated that around one in five people will suffer from a bout of depression at some point in their lives.
For those with mild or moderate depression or anxiety, psychological therapies should be tried before doctors prescribe medication.
But lack of access to therapy means GPs often have to give antidepressants because there is no other treatment.
Current waiting lists for cognitive behaviour therapy (CBT) can be months, or even years.
Two computer programmes have been approved for use in the NHS - Fear Fighter for treating people who have phobias or suffer from panic attacks, and Beating the Blues for treating people with mild to moderate depression.
In Beating the Blues, patients do eight one-hour sessions, learning how to challenge unhelpful thoughts and deal with stressful situations.
Some areas of the country are already using the programmes, but from April all primary care trusts will have to provide computerised CBT for patients who may benefit.
Health Secretary Patricia Hewitt said: "On 1 April, we will reach the first milestone in our drive to provide choice - namely quicker access to computer-based self-help services to stop mild mental health problems becoming worse.
"Clinical evidence confirms that counselling and therapy are just as effective as medication in helping to treat most cases of depression."
Paul Farmer, chief executive of Mind, said computerised CBT was an important addition to the range of treatment options available for people who suffer from mild depression or anxiety.
But he added: "This method of delivery will not suit everyone.
"Some people will prefer face-to-face contact and this electronic therapy must not be a replacement for CBT."
Dr Richard Vautrey, GP negotiator for the British Medical Association, said it was helpful to have a range of options for treating depression and computerised CBT had proven to be useful in some areas of the country.
But he added: "Many patients still struggle to get an appointment with a therapist and it is key that it doesn't replace the pressure to invest in trained therapists."
Marjorie Wallace, chief executive of the mental health charity Sane, said: "Evidence from several hundred thousand of our callers shows that of those reporting depression or anxiety, while 83% are being treated with medication, only 2% are receiving cognitive behavioural therapy.
"While we applaud the secretary of state's announcement, we urge her to match it with a funding commitment to ensure that CBT can be a real choice, as she intends, for everyone who could benefit."