The article analyses output gap values published by the Czech National Bank, the Ceska Sporitelna, and deals also with some output gap estimates of private persons. The Czech National Bank publishes its estimates in Inflation Reports. Ascertained data uncertainty is significant; it commonly exceeds one percentage point. The Ceska Sporitelna publishes its output gap estimates in its publication Quarterly Analysis: Economics in Detail. Published time series are yet short. Nevertheless, the error rate increases so far. Unofficial estimates made by various methods are also very different. Confidence bands are so wide that very little can be said about true output gap value.