BACKGROUND: Malignant neoplasms of the lymphoid or myeloid cell lines including lymphoma, leukaemia and myeloma are referred to as haematological malignancies. Complementary and alternative treatment options such as meditation practice or yoga are becoming popular by treating all aspects of the disease including physical and psychological symptoms. However, there is still unclear evidence about meditation's effectiveness, and how its practice affects the lives of haematologically-diseased patients. OBJECTIVES: This review aims to assess the benefits and harms of meditation practice as an additional treatment to standard care for adults with haematological malignancies. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL, Issue 8, 2015), MEDLINE (1950 to August 2015), databases of ongoing trials, the metaRegister of Controlled Trials (mRCT) (http://www.controlled-trials.com/mrct/), conference proceedings of annual meetings of: the American Society of Hematology; American Society of Clinical Oncology; European Hematology Association; European Congress for Integrative Medicine; and Global Advances in Health and Medicine (2010 to 2015). SELECTION CRITERIA: We included randomised controlled trials (RCTs) using meditation practice for adult patients with haematological malignancies. DATA COLLECTION AND ANALYSIS: Two review authors independently extracted data from eligible studies and assessed the risk of bias according to predefined criteria. We evaluated quality of life and depression. The other outcomes of overall survival, anxiety, fatigue, quality of sleep and adverse events could not be evaluated, because they were not assessed in the included trial. MAIN RESULTS: We included only one small trial published as an abstract article. The included study investigated the effects of meditation practice on patients newly hospitalised with acute leukaemia. Ninety-one participants enrolled in the study, but only 42 participants remained in the trial throughout the six-month follow-up period and were eligible for analysis. There was no information provided about the average age and sex of the study population. We found a high risk for attrition bias and unclear risk for reporting bias, performance and detection bias because of missing data due to abstract publication only, thus we judged the overall risk of bias as high. According to the GRADE criteria, we judged the overall quality of the body of evidence for all predefined outcomes as 'very low', due to the extent of missing data on the study population, and the small sample size.As the abstract publication did not provide numbers and results except P values, we are not able to give more details.Meditation practice might be beneficial for the quality of life of haematologically-diseased patients, with higher scores for participants in the mediation arms compared to the participants in the usual care control group (low quality of evidence). Levels of depression decreased for those practising meditation in both the spiritually-framed meditation group and the secularly-focused meditation group in comparison to the usual care control group, whose levels of depression remained constant (low quality of evidence). The influence of meditation practice on overall survival, fatigue, anxiety, quality of sleep and adverse events remained unclear, as these outcomes were not evaluated in the included trial. AUTHORS' CONCLUSIONS: To estimate the effects of meditation practice for patients suffering from haematological malignancies, more high quality randomised controlled trials are needed. At present there is not enough information available on the effects of meditation in haematologically-diseased patients to draw any conclusion.