The singer, who has daughter Lily Rose, 12, and son Jack, nine, with Johnny Depp, said that she has kept almost every outfit that she has ever worn.
She told Vogue magazine, 'I keep everything. It's not a good thing because you drown under your closet, but some things are really important to me, especially the stage clothes.'
And her most treasured possession is a vintage velvet dress, although it's literally hanging on by a thread.
'The dress is from the twenties. And it's not good to perform in because it's so fragile. I've almost ripped it so many times,' she said.
'It smells vintage so you can't wash it the way you would want.
'But it has the best appearance, the way it catches the light, the way it moves.'
The 38-year-old added that texture comes before style when it comes to picking her clothes.
'I love to be comforted by clothes. Obviously you want to look in the mirror and like what you see but I need to love what I feel. I need to feel comfortable in terms of sensation,' she explained.