The 'Can't Fight the Moonlight' singer is to tie the knot with fiance Eddie Cibrian later this year and has been inquiring about a number of venues in the mountainous US state.
A source said: "LeAnn has approached a number of owners of private ranches about a May or June wedding."
LeAnn and Eddie took a romantic break in Montana last August so it is place close to both of their hearts.
She wrote on her twitter page at the time: "Going to lock myself up in my cabin with Eddie Cibrian, if you know what I mean.
"Montana is the most peaceful and beautiful place I could be [with Eddie] right now. We have NO service other than the main lodge where we are staying, so we are escaping . . . Montana is magical! Peace it brings! (sic)"
LeAnn, 28, confirmed her engagement to 37-year-old Eddie over the Christmas period after he proposed while they holidayed in Los Angeles.
She tweeted: "For those who haven't read, Eddie and I got engaged over the holidays. That's the news. It's for real this tine and the first time EVER!
"Thank you for all your well wishes!! We are extremely excited and look forward to a beautiful future. It's been an incredible last few days, I was shocked!!! We are blessed, our families are so happy and our lives are filled with love. (sic)"
LeAnn met Eddie when they worked on TV movie 'Northern Lights' in 2008 and were both married to other people.
The singer-and-actress' admission to an affair with Eddie was unpopular with many of her fans, but her divorce was finalised in June and ex-husband Dean Sheremet has since got engaged again.
Eddie has two children - Mason, seven, and Jake, three - with his ex-wife, make-up artist-and-model Brandi Glanville.