Leo's two doctors, Luigi Carbone and Stefano Margaritora, provided a medical update on Wednesday.
Blood tests and a chest X-ray confirmed a normal post-operative recovery, with levels within the norm, they said.
"The Holy Father underwent respiratory physiotherapy and has begun walking in his room. He resumed his regular diet and had breakfast and lunch," they reported.
"Recovery is proceeding as planned."
The Vatican said the Pope spent a peaceful night in Rome's Gemelli hospital after doctors removed the lower lobe of his right lung and confirmed he has cancer.
Experts said further tests are needed to know if the disease has spread and if more treatment is needed.
The surgery showed the 71-year-old pontiff has the most common type of lung cancer, known as lung adenocarcinoma, the Vatican said in a medical bulletin late Tuesday.
The Vatican said the surgery lasted approximately 90 minutes and was successful, with no complications.
The press office pointed to the medical statement's mention of the "radical" removal of the lobe as an indication that doctors took out all suspect tissue in hopes of removing any lingering traces of the cancer.
The right lung has three sections or lobes while the left has two.
After one lobe is removed, the rest of the lung can gradually compensate, especially in otherwise healthy and physically active people.
Leo is known to be sporty, with weekly tennis games and swimming.
The Vatican added the Pope celebrated mass with his secretaries on Wednesday afternoon in a special chapel set up for him on the 10th floor of the hospital.
US President Donald Trump said he hoped the Pope would "get better fast."
"I want to see Pope Leo get well," Trump told reporters in Arizona. "I just want to wish him well, get better fast."
Trump also said the Pope's prognosis that he had heard about appeared encouraging, while acknowledging the seriousness of a cancer diagnosis.
with Reuters
