In a printer, a controller determines a type of print medium currently mounted in a mount portion, and acquires a first set of print data correlated with a first medium type and a second set of print data correlated with a second medium type. In a case that a print medium of the first medium type is mounted in the mount portion, a print portion prints a first print image based on the first set of print data, and thereafter prints a second print image based on the second set of print data. In a case that a print medium of the second medium type is mounted in the mount portion, the print portion prints the second print image based on the second set of print data, and thereafter prints the first print image based on the first set of print data.