The troubled actress, who has gone from starlet status, via jail, to the pages of Playboy in a few short years, was particularly troubled by the Australian actor's death in 2008.
The diary entries, reported in the Daily Mail, reveal Lohan's despair that "I'm in love with him... I want to hear him laugh and hold me. I crave his touch and care."
And they also hint at a relationship between the pair, with Lohan writing of her "need to be held in the arms of someone who understands. But what do you do when the one who understands is gone?"
Ledger died of a prescription medication overdose in January 2008, six months after he separated from actress Michelle Williams, mother of his daughter Matilda.