Roma finished sixth in Mourinho's first campaign in charge last season and won the inaugural UEFA Conference League by beating Feyenoord.
The Giallorossi have made some shrewd signings for the new season, bringing in the likes of Mile Svilar, Zeki Celik, Nemanja Matic, Paulo Dybala and Georginio Wijnaldum to the Stadio Olympico.
An impressive pre-season saw Roma defeat the likes of Tottenham Hotspurs and Shakhtar Donetsk and they opened their Serie A campaign with a 1-0 win away at Salernitana on Sunday.
The positive results have led to suggestions that Roma could have a say in the Serie A title race but Mourinho believes that is an exaggeration.
The Roma head coach told reporters over the weekend: "There are teams that have an economic potential that is not comparable, I'm not saying the distance between Earth and Mars, but there are people who spend €100-150million per season.
"We go play and do the best we can. In the championship we finished in sixth place, our squad improved, we lost Mkhitaryan and Veretout, but we took on players with whom we improved, but other clubs also did.
"For this reason, during this period where I didn't need to talk to journalists, it amazes me when it comes to us in one way, but not about the others. Roma can be a candidate for the Scudetto if they have won 18 titles.
"Only Sampdoria and Lecce spent less than us. Milan and Inter finished with 25 and 23 points ahead of us and improved. There is a lot of noise around us for an interesting match against Tottenham and Shakhtar.
"We talk about us, while there is silence around other teams. Lazio spent €39 million, are they candidates for the Scudetto?"
