It is estimated almost one in five NI people have a fear of going out to such an extent that if affects their ability to function, says a leading charity.
Agoraphobics can feel trapped by their condition
A new bus advertising campaign aims to raise awareness of a helpline for people with phobias.
Delia McCartan of the Northern Ireland Agoraphobia and Anxiety Society said a certain amount of anxiety and fear was normal.
However, people with phobias will sometimes have panic attacks.
"When people suffer panic attacks they actually feel that they are going to have a heart attack," said Ms McCartan.
"That is how it feels to them.
Delia McCartan says helpline will offer victims support
"They will get someone on the end of the helpline who understands that, who can listen to them and support them.
"They can give them advice and explain to them that what they are feeling is normal and will pass.
"They will perhaps help them with breathing techniques to get them through that sense of fear and that sense of panic."
The helpline number is 0845 122 8630.