Men showed a sentimental side in a survey that found they are more likely to hoard love letters, mementoes and photographs from previous relationships than women.
Over a third (36%) of British adults confessed to secretly squirrelling away keepsakes from past relationships, the Wilkinson survey found.
And men are more likely to do so - a third admit stashing photos of old flames, compared to just a fifth of women, while a quarter of men admit hanging on to love letters and mementoes, compared to a fifth of females.
Younger people were more likely to keep a secret stash, with 53% of under-35s hoarding items from old relationships.
A third of people said they kept mementoes from old relationships to remind them of happy times, and the majority (70%) told researchers their partner or spouse would be angry or upset if they found out. But over half (52%) said the items were part of their history and they could not bear to part with them.
People were more likely to tell their friends than families about their secret hoards - six out of 10 said they would be embarrassed to tell their friends while three-quarters said the same of their parents.
Out of the 2,000 people surveyed, almost two-thirds (63%) of men described themselves as sentimental, rising to four-fifths of females.
Newcastle is the secret hoarding capital of the country, where almost half (45%) of residents admit to keeping items their partners do not know about, followed by Leeds (41%) and London (39%).
Graham McLaughlin, of Wilkinson, said: "These are very interesting figures that may surprise people as they reveal a more sentimental side to men than many previously believed. Both sexes are guilty of secret hoarding but the fact is men are actually more secretly sentimental than women, and a greater number keep hold of items of emotional significance.
"It is obvious that many people feel compelled to store their memories but they are doing this in a very personal way. However you do it, memories form such a significant part of your history and nobody can take them away from you. And you can guarantee that the majority of items that are stored in secret are actually quite harmless, that they are simply pleasant reminders of the past."