IT’s both the best AND worst of times for QUEEN LATIFAH.

The rapper/actress is basking in the success of her syndicated gab-fest, “The Queen Latifah Show” – but at the same time she’s reeling from a family crisis.

Her beloved mother, Rita Owens, is battling deadly lung cancer.

“Latifah is all smiles and laughs on her new show, but it’s all a front,” said a close pal. “She’s in tears almost every day after she finishes taping.”

The 43-year-old former Jenny Craig spokes-person is making sure her mother receives the best medical care money can buy. She’s even moved Rita from her home in New Jersey – the house where Latifah was raised – to Los Angeles, so she could be close to her as she fights the often fatal disease.

“Latifah goes through the motions at the TV studios, but as soon as the show is taped and the last production meeting is over, she’s out the door, rushing home to her mom,” the pal said.

According to the source, Rita, 64, started experiencing shortness of breath and exhaustion early last year. After undergoing tests, doctors confirmed she had lung cancer.

The illness is taking a toll on the former high school teacher. A source says she’s lost a great deal of weight and is now on oxygen and confined to a wheelchair.

“Rita smoked in the past but she stopped a long time ago,” the family insider continued, “so it was shocking when she was diagnosed with lung cancer.”

This isn’t the first heartbreak for Latifah, whose real name is Dana Owens. Her parents divorced when she was 9, and her older brother, Lancelot Jr., died in a motorcycle accident in 1992, not long after Latifah gifted him the bike. In 1995, a friend was shot and critically wounded during a carjacking of Latifah’s BMW in Harlem. She fell into a deep depression that led to drug abuse, which she has since overcome.

“Latifah says her mother is amazing,” noted the insider. “She goes through her chemotherapy treatments without complaining, has such a positive outlook on life and always wants to make sure everyone else is OK.

“Right now, Latifah is praying for her mother’s health, even though she knows that the prognosis for lung cancer is not always positive.”

While Rita is putting up a brave fight, the insider says she’s preparing her daughter for the worst.

“Latifah promised Rita that she’ll be strong,” the insider added. “And she’s making sure every day she has with her mother is special.”