Summary This study evaluated and compared the effectiveness of two different off-season, short-term basketball training programs on physical and technical abilities of young basketball players. Twenty-seven adolescent basketball players (14.7±0.5 years; Tanner stage: 3.5±0.5) were randomly divided into a specialized basketball training group (SP, n =10), a mixed basketball plus conditioning training group (MX, n =10) and a control group (n =7). Training included five sessions per week (100–120min each) and was performed for 4 weeks. Maximal oxygen uptake was similarly improved after SP (4.9±1.8%) and MX (4.9±1.4%), but there was no effect on ventilatory threshold. Peak and mean power output measured during the Wingate test were also improved by a similar magnitude after SP (21±5%) and MX (15±6%). Trunk muscle endurance was equally increased (SP: 23±4%, MX: 25±5%), but arms endurance was improved significantly more after MX (50±11%) compared to SP (11±14%, p <0.05). Performance in four basketball technical skills was similarly increased (by 17–27%) in both groups, with a tendency for greater improvement of the SP groups in the technical skills of shooting and passing. These results indicate that a SP basketball training program, performed exclusively on-court was as effective as a MX training program in terms of aerobic and anaerobic fitness improvement. Furthermore, the decrease of the total on-court training time in the MX group resulted in a tendency for a smaller improvement of basketball technical skills. In conclusion, both SP and MX training are equally effective in order to limit and/or reverse the detraining effects that occur during the off-season in basketball.