Police want to track down a novice graffiti artist who has been making his mark around Highfield.
It has defaced fences, garage doors and electricity boxes in recent weeks.
Neighbourhood PC Steven Alison said: “We will not tolerate this type of behaviour in Hemel Hempstead. We want people to enjoy the area in which they live and not be blighted by such reckless acts of damage.
“I’d encourage anyone who may know who is responsibly for this graffiti to contact the safer neighbourhood team as soon as possible via the non-emergency number 101.
“I’d also urge parents to be aware of the warning signs that their child could be involved in graffiti, such as leaving home with marker pens, graffiti on school books and leaving home with bags etc.”