There is for the PlayStation Portable (PSP) because Rockstar Games never released a port for that system. The technical requirements for Grand Theft Auto IV

The PSP hardware, while revolutionary for its time, simply lacked the processing power, RAM, and storage capacity to run the RAGE engine that powered GTA 4's physics and high-definition graphics. While the PSP saw three incredible GTA titles ( Liberty City Stories , Vice City Stories , and Chinatown Wars ), GTA 4 was a leap into the next generation of consoles that the handheld couldn't bridge. What are "GTA 4 PSP ISO" Downloads?

If you want to play Grand Theft Auto on the go, consider these legitimate options: Official PSP Titles Liberty City Stories Vice City Stories Chinatown Wars

While there is no official port, the modding community has attempted some wild projects. These are not ISOs you simply drag and drop; they require extensive technical knowledge.