Householders living in the UK have admitted they have not been using the space available in their homes effectively, the study commissioned by Ikea has revealed.
A sixth of the 2,000 people surveyed by One Poll said they spent an average of £35 a year each on extra storage facilities.
Men typically spend £43 each, whereas women pay out £27 a year trying to find a place for all their furniture and belongings, the study said.
Londoners are the biggest storage spenders, paying £49 a year to stow their belongings, it said.
Residents in the south west spend the least, at £24 per person, according to research.
The UK has the smallest homes in Western Europe with an average living space of just 85 square metres, an Ikea spokesman said.
The nation's lack of square metres is compounded by poor spatial skills with 46% of people claiming they have trouble visualising the space and room they do have available, he added.
The areas most likely to go unused are in the loft, under the stairs, in the eaves, hallways and on the landings, the survey said.
"That said, sometimes people can be a bit too quick to rush out and hire additional storage.
"Families could be wasting millions each year simply because they don't have great spatial awareness skills and don't always know how to make the most of the space that they have."
Naomi Cleaver, an interior designer and television presenter, said: "When it comes to maximising the space in which we live, as a nation we seem to lack a proper understanding of size and how best to use it.
"By thinking carefully about the room, combined with some smart furniture choices and off the floor storage options, people can quickly utilise areas of dead space, rather than spending their hard earned cash on needless outside storage."
To see the research findings visit www.ikea.co.uk/smallspaces.