The use of “gaseous molecule surrogates,” which can produce gaseous compounds by chemical reactions or physical stimuli, has been attracting attention as a beneficial tool to realize safe and convenient organic synthesis. We have engaged in the development of novel surrogates of gaseous molecules, especially focusing on carbon monoxide (CO), and in their application to synthetic organic chemistry. This article describes our recent progress on the development of catalytic organic reactions utilizing gaseous molecule surrogates with high safety and practicality. Detailed mechanism of CO generation from phenyl formate as a CO surrogate has been elucidated both experimentally and theoretically, which led us to develop a series of Pd-catalyzed carbonylative reactions such as room-temperature alkoxycarbonylation and rapid fluorenone formation. We have also exploited the novel synthetic role of potassium metabisulfite as a sulfur dioxide (SO2) surrogate to selectively afford sulfur-containing compounds with various valences, based on achieving the selective formation of cyclic sulfonamides and sulfinamides, symmetrical sulfones, and symmetrical sulfides. It is noteworthy that newly developed modular synthesis-like reactions utilizing both CO and SO2 surrogates were safely conducted with ordinary glassware and were scalable to gram-scale production without any difficulties, indicating their potential use on facile derivatization in medicinal chemistry and on large-scale synthesis.