Objective　To　explore　working　memory　and　the　ability　to　process　different　emotional　stimuli　in　patients　with　first-onset　and　untreated　minor　(mild　or　moderate)　depression.　Methods　Patients　with　first-onset　and　previously　untreated　minor　depression,　and　healthy　controls,　were　enrolled.　Using　a　modified　Sternberg　working　memory　paradigm　to　investigate　the　combined　effects　of　emotional　stimuli　with　working　memory,　participants　were　exposed　to　experimental　stimuli　comprising　pictures　that　represented　positive,　neutral　and　negative　emotions.　Working　memory　ability　was　measured　using　reaction　time　and　accuracy,　and　emotion-processing　ability　was　measured　using　pupil　diameter.　Results　Out　of　36　participants　(18　patients　with　minor　depression　and　18　controls),　there　were　no　statistically　significant　between-group　differences　in　response　time　and　accuracy.　Positive　stimuli　evoked　changes　in　pupil　diameter　that　were　significantly　smaller　in　patients　with　minor　depression　versus　controls,　but　changes　in　pupil　diameter　evoked　by　negative　stimuli　were　not　significantly　different　between　the　two　groups.　Conclusions　Healthy　subjects　showed　a　stronger　emotional　response　to　positive　emotional　stimuli　than　patients　with　first　onset　and　previously　untreated　minor　depression,　but　there　were　no　differences　in　response　to　negative　emotions.　There　were　no　statistically　significant　between-group　differences　in　terms　of　speed　of　cognitive　response,　but　this　may　have　been　due　to　the　relatively　small　samples　sizes　assessed.　Studies　with　larger　sample　populations　are　required　to　further　investigate　these　results.