Summary form only given. Time-resolved photoluminescence and pump-probe spectroscopies have been employed to study the spin relaxation processes of excitons in bulk semiconductors and semiconductor quantum wells (QWs). Extensive studies have shown that the spin dynamics in QWs differs from that in the bulk. In spite of many studies on excitons with large Bohr-radius such as in GaAs-based QWs, studies on excitons with small Bohr-radius are lacking. Since spin relaxation greatly depends on the exchange interaction between electron and hole in the exciton, the spin dynamics is expected to change with the coupling strength between the electron and hole. Therefore, experiments for excitons with small Bohr-radius are desired for full understanding of spin phenomena in QWs.