Demi Lovato ''can't believe'' her father has been dead for a year.

The 21-year-old singer, who was devastated when Patrick Lovato passed away on June 22, 2013 after battling cancer, posted a touching tribute to him on Twitter on Friday (20.06.14).

The 'Heart Attack' hitmaker tweeted: ''Can't believe it's already been a year.. Wish I could've hugged you one last time.. RIP Daddy, I love you.''

She also posted a collage of photographs of herself and Patrick from when she was a little girl.

Demi previously admitted laying her dad to rest was ''the hardest thing'' she had ever done, but felt an ''overwhelming sense of peace'' after his funeral.

She tweeted at the time: ''Today I put my Daddy to rest.... hardest thing I've ever done.. But I know great things will come of this...

''There's an overwhelming sense of peace knowing my dad is no longer battling his demons anymore and that makes me so happy.''

The singer, who was raised by her mother, Dianna, and stepfather, Eddie De La Garza, after her parents split in 1994, had a strained relationship with Patrick at times, but after his death she said: ''I'm handling it okay, my father and I didn't have the most ideal relationship. But at the end of the day, he's still my dad and I grew up with him and he's a wonderful person. It's difficult...I'm handling it okay.''

She later said: ''My dad suffered from severe mental illness so at least there's peace in knowing he's not suffering anymore.''