COMO House visitors have reported seeing a young girl in one of the rooms.

Nothing surprising about that, except the girl has been dead for 133 years.

Ethel Armytage was seven years old when she died of diphtheria in 1872 at the South Yarra mansion, where her family lived.

She was "seen" in Como's morning room by a startled mother and daughter visiting the property to plan a wedding.

Visitors also reported seeing a card, exhibited in the museum collection, moving around its display case by itself.

It is one of the first paranormal experiences with Ethel.

Most spooky sightings at the house have been of Ethel's mother Carolyn, who died, aged 77, of a heart attack in an upstairs bedroom in 1909.

Como wedding co-ordinator Anna Tavrou, who was with the tour group that saw Ethel's ghost, said sightings had become common and volunteers often heard "things go bump in the night".

"It's all right, because it's a friendly ghost, although it understandably gave the lady who saw her quite a fright," Ms Tavrou said.

The sighting, however, had not put them off having the wedding at the property, she said.

Ms Tavrou said a number of her volunteers had seen ghosts. "It's part of working in a historic property like this," she said.

"One volunteer was here late at night when the lights started flicking on and off."

National Trust spokeswoman Pauline Hitchins said ghosts were regularly reported at Trust properties every year.

"None of them are nasty ghosts," Ms Hitchins said.

"It's not uncommon for old properties to have ghosts - some people are just more prone to seeing them than others."

Ghost hunter Drew Sinton said he had heard reports of lights turning on and off, mysterious cool breezes and a blind cord swinging in Ethel's bedroom.

"People think ghosts are only there because they have unfinished business, but sometimes they stay because they feel at home in a certain place," he said.

Mr Sinton said ghosts appeared at any time of the day or night.

"I have had hard-nosed atheists or sceptics who have had ghostly experiences and it's completely changed their opinion," he said.

"Soldiers, cops, nurses - and even advertising executives have reported seeing ghosts."